Natural vs Enhanced: Navigating Lapidary Materials

Helen Serras-Herman FGA guides us through the varieties of all-natural and enhanced gem materials, highlighting key treatments and their impact on the marketplace. 

There is an endless inventory of lapidary gem material on the market today, created or enhanced to look like other natural materials, usually one that is rare and expensive. Most of these enhanced materials are natural materials that have been dyed or compressed to simulate a better quality material, while some are partly natural stone and partly other materials, such as resins and metals. There are also natural materials that have been dyed to a completely different colour in order to look like another natural material, which we could call ‘look-a-likes’. All these simulants provide an inexpensive alternative to natural gems, and many of them are beautiful, with bold patterns and durability. 

The only problem surrounding these stones is disclosure, or the lack of it. Dealers should always let their customers know exactly what they are buying. Even though many times the original wholesaler or lapidary may have disclosed information about the nature of the rough, cabochons or beads, somewhere down the line, or online, information gets buried or blurred. 

One of the reasons for disclosure, besides honesty, is for the customer to know how to take care of the finished stones. The customer may be the lapidary, designer, metalsmith, the final jewellery client or collector. Disclosure helps determine how well stones will wear once set into jewellery, whether they should be set into rings (which take more abuse) or pendants and brooches, or how will they survive in an ultrasonic cleaning machine. 

Turquoise Sky necklace made by Helen Serras Herman.
Turquoise Sky necklace made by Helen Serras Herman: The carved turquoise in this 'Turquoise Sky' pendant, set in sterling silver with orange sapphires from Montana, is from the Hatchita Mine in Southwestern New Mexico, showing natural beautiful golden-colour matrix inclusions.

According to the Federal Trade Commission (FTC) guides for the jewellery industry, with the exception of normal fashioning (cutting and polishing), it is the seller’s responsibility at all levels of commerce to clearly disclose to the buyer at the time of the sale whether the stone is natural or not, and about any enhancements. 

While many articles focus on disclosure of enhancements of faceted rubies, emeralds or diamonds, the cabochon and bead market slides almost quietly under the disclosure radar. 

NATURAL TURQUOISE VS STABILISED & COMPRESSED TURQUOISE 

Turquoise is a beautiful gemstone found in several places around the world. As one by one the famous Arizona turquoise mines close - Bisbee, Sleeping Beauty - there are not too many options left to source the all-natural material, which is sought after and appreciated by lapidaries, gem collectors and jewellery lovers alike. Hard, all-natural turquoise is probably less than 3% of all turquoise sold today. 

The vast majority of turquoise on the market has been stabilised with polymers in order for the stone to harden, a permanent treatment. When dyes are added to the resin, the turquoise is referred to as ‘treated’ instead of ‘stabilised’. 

Blocks by Colbaugh Processing Inc.
Blocks by Colbaugh Processing Inc. A variety of compressed natural turquoise blocks is offered by Colbaugh Processing, including turquoise with bronze, Mohave purple turquoise with and without bronze, and Mohave green turquoise with and without bronze. 

A rarer form of turquoise comes in a compressed type. Small, natural nuggets of quality turquoise are compressed with resin into blocks. The outline of each nugget is still visible. There are no dyes in these blocks. These blocks are created by Colbaugh Processing Inc, a very-well known company owning the only active mine for turquoise in Arizona, the Kingman mine. They also create compressed blocks of natural turquoise nuggets infused with bronze or zinc that offer a very unique look, simulating natural turquoise with golden web inclusions. A dyed bright green turquoise block is also available, with or without infused bronze, simulating the rare bright green gaspeite from Australia. 

NATURAL LAPIS VS ENHANCED VS SIMULANT 

Lapis Lazuli is a striking rich blue opaque rock, composed of several minerals; lazurite, calcite veins and pyrite crystals are the most predominant. There are only a few well-known mining areas in the world producing fine quality lapis: Russia, Chile and Afghanistan, and they are all ancient deposits. 

Magnesite (left) vs. lapis lazuli (right)
Magnesite (left) vs. lapis lazuli (right)

Pale and mottled material is successfully marketed as ‘Denim lapis’. Lapis should be kept away from heat and chemicals, especially in the event that the stones, carvings or beads may be dyed. Simulants include a brightly-coloured man-made lapis crushed for inlays, and magnesite from China, a soft and porous material, dyed blue with added metallic inclusions that simulate pyrite, that truly looks like natural lapis. 

RAINBOW CALSILICA 

Rainbow Calsilica is a manufactured material created and sold by Colbaugh Processing Inc. The material imitates natural quartz with veins of blue chrysocolla and red jasper found in copper mines in Arizona. This colour combination is rare making the natural pieces highly prized. 

Rainbow Calsilica, natural vs. man-made.
Rainbow Calsilica, man-made (left) vs. natural (right): Rainbow Calsilica is a manufactured material made of pulverised calcite mixed with pigments and stabilised with a polymer, imitating quartz with veins of blue chrysocolla and red jasper.

Tests were undertaken on samples of Rainbow Calsilica at the SSEF Swiss Gemmological Institute laboratory in Basel in 2002. Their final report, as referenced in the GIA’s Gems & Gemmology magazine in 2002, states that “the samples examined appear to have been made of pulverized carbonate rock (calcite) mixed with pigments and stabilised with a polymer.” 

CONCLUSION 

As lapidaries, designers and collectors, we always look for new gem materials to incorporate into our artwork. The list of all natural materials is shrinking daily, and the variety of enhanced lapidary materials on the market today is almost overwhelming. 

The better we understand these materials, the better we will be able to sell them to our customers. Today’s gem and jewellery consumers are educated, and look up to artists and jewellers to alert them about the natural origin of the materials or the technological enhancements that made these lapidary gem materials available, affordable, durable and appealing. ■ 

Gem-A members can log in to read the full article Gems&Jewellery Spring 2017 / Volume 26 / No. 1

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image Mohave purple turquoise blocks: Mohave purple turquoise has become very popular and is made from natural turquoise compressed with resin, then dyed and stabilised. All images by Hellen Serras-Herman. 


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


 

Additional Info

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A Man of the Ocean: Diving for Organics with Eric Fritz

In a recent trip to the London headquarters, Eric Fritz, FDGA DGA manager of North America for Gem-A stopped by for an industry insider Q&A, educating us on theoretical and practical guidance of organic materials. Sarah Salmon speaks to the man of organic passion exploring the nature of these beautiful materials.

With a passion for pearls, a deep love for shells since the age of four and an extensive knowledge of coral, minerals and gemstones, Eric Fritz reveals his top tips when it comes to his specialty: organic gem materials.

Q. When identifying pearl, what are Gemmologists looking out for when grading their quality?

For value, you will be looking at whether it is a salt-water or freshwater pearl, whether it is natural - formed without any human involvement - or whether the pearl has been cultured. The most valuable in terms of quality across the board would be natural saltwater pearls. This would then be followed by natural freshwater pearls, saltwater cultured pearls to freshwater cultured pearls.

Roundness is also preferable when grading a pearl where the more perfectly round and larger it is without blemishes, the more precious it is considered. The bigger the pearl, provided it still has a good ‘roundness’ and lustre finish to it with minimal spots and blemishes to it, the more desirable and valuable it becomes.

Q. What causes the blemishes and imperfections to form on a pearl?

The blemishes are caused by the formation of the organic material itself. Formed by living organisms which, just like us are made up of a range of different imperfections, gives each pearl its unique, flawed composition. The living environment of the shellfish is also a key factor where surrounding waters may contain disease or the shell mechanism itself may malfunction; all of which directly affects the pearl quality.

Q. Where in the world are the most desirable pearls located?

Probably the most desirable and rarest natural pearl will always be the mellow mellow pearl. This is a yellow - golden range commonly found in Myanmar, Burma and Vietnam. The mellow mellow pearl is often hailed as the holy grail of all pearls due to being that of the most value.

The price of a pearl can vary widely in correlation to its size, ranging from $3000 to $65-70,000 at many Gem trade shows, even when such pearls contain blemishes and are therefore still considered imperfect

Q. We often hear about Mikimoto pearls, is this a particular brand or is it a type of organic pearl?

Mikimoto was the first person to commercially produce cultured pearls in Japan in the late 1800’s. Prior to this, cultured pearls had only been produced on an experimental basis but Mikimoto found a technique that he could use to sustainably produce small cultured pearls – typically 7mm - in small saltwater shells.

Its predecessors, being Gem-A, launched the first global Gem lab in London in order to differentiate cultured Mikimoto and natural pearls. The value of each was quite starkly different which meant that many London jewellers became concerned at the introduction of cultured pearls against the trade of more expensive natural pearls. Mikimoto, dating back over 100 years was, and probably still is, the top quality Japanese Akoya pearl on the market.

Q. Being similar in name, what is the key difference between a conch shell and a conch pearl?

Great question! The Conch shell, Lobatus Gigas being its scientific species, occurs only in the Caribbean off the coast of North America, from Florida down through to the West Indies. It is a big shell that was originally gathered by the native people for food due to its very large edible muscle. It is said that 1 in a hundred conch shells could produce a pearl. Conch pearls come in a range of colours from whites to pinks to browns and yellows but it is the pink variety that remains to be the most valuable. We often believe that the very inside of the Conch shell is pink in colour which is why the pink pearl remains the rarest.

However it is also the inside of the conch shell that produces all of the varying colours of conch pearls. Imitations are created when people take the conch shell and try and cut around a bead, passing it off as a genuine pearl. However, these imitations always have concentric bands where, if you look at the side of the bead, you will see what looks like tree ring growth around the edges. This is a kay indication that this is not a real pearl, but an imitation that has been cut out of a shell.

Q. With a huge variety on the market, how do you identify and compare different seashells from one another?

Seashells come in such a wide variety of genus, ranging from freshwater to seawater environments. Dating back to the Victorian times, seashells were and still are highly collectable objects of nature. Linnaeus, founder of the Linnaeus society extensively named over half of the shells we have identified so far. Seashells are very easy to tell the different species apart as they visually look very different from one another.

Today however to differentiate shells via its species level, identification can require DNA analysis to indicate the differences from one shell to the next. They may look very similar but there is stark variation between the different species.

Q. If you’re looking to purchase a high quality shell, what attribute should one be looking for?

People are attracted to different shapes and colour forms with some buying what we call ‘valves’ where two halves of a shell are held together by a muscle, whilst others favour gastropods where the shell is one piece. Some people like to collect a whole family of shells, preferring only to select pieces within the same genus of shells, leading to a lot of variability. Shell prices for collectors range from £2-£3 up to £100,000 for those that are highly desirable.

Q. What are the key differences between 'hard' and 'soft' coral?

A lot of the time when you look at soft corals in its natural habitat under water, they can often look like plants or sea fans which move with the ocean current. They can range in appearance from big broad fans to tall upright branches but most tend to move. Hard coral contains more calcium carbonate than soft and are often what we refer to as coral reef. An expansive garden of skeletons makes up the coral bed where tiny living organisms live within the pores of these hard corals.

Q. Where is Coral found in abundance across the world?

Coral is most commonly found within temperate waters, including the Caribbean, Australia and the Pacific, with its particular type ranging from place to place. Coral will vary widely in habitat from shallow 3-5ft soft coral waters to deep hard coral found over 1000m underwater. The most precious coral for jewellery is the red coral of the Mediterranean, originally found 100ft under water by early fishermen.

This precious coral was thought to be extinct until divers located caves as shallow as 10-12ft containing this red coral species.

Q. So if you’re looking for a piece of jewellery containing red coral, how do you identify it as genuine and not an imitation?

Corals are fairly easy to differentiate with most of the corals – the precious corals – having visible striations that move across the stone/bead. This identifies the growth where the small tree -like structures were with vertical striations of the stems. Many corals are treated with dye to enhance their appearance so being aware of this when purchasing coral is important as those that have been dyed are no longer considered precious. Dyed coral can be identified when a concentrated colour is found along the edges of the stone where the dye has run in a cut stone or if the coral itself is a perfectly uniform colour without imperfection.

Coral value is similar to pearl where the more intense the colour, like red, the more valuable the material is deemed to its pink and orange counterparts.

Q. Final question, I promise! Out of pearl, coral and shell, what is your favourite organic material and why?

That’s a hard one! I have a much more extensive collection of shells since I started collecting them at only 4 years old on the coast which continues till today. In this case, since I’ve been interested for over fifty years, I would probably have to say shells. I collect two main families, the Cowrie shells as well as Conch shells of which The Queen conch is one of them. It was from collecting shells that I got to love pearl, especially as I am yet to find one. The question is tricky as the pearls live inside the shells which then live beside the coral so they are all connected!

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image of Coral Skeleton and Pearl. All images courtesy of Henry Mesa, Latin American Ambassador at Gem-A.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


Additional Info

Read more...

Rio Tinto Reveals The 2.11ct Argyle Everglow Red Diamond

It is always an exciting time of year when Rio Tinto unveils what has been discovered at its Argyle diamond mine. Typically, this is beautiful pink diamonds, with the occasional purplish violet tones. Even rarer still are the fancy red diamonds, which remain a mysterious quantity even today. 

It is without doubt that red diamonds are some of the most beautiful and captivating gemstones, largely due to their extreme rarity. In fact, it has been estimated that as few as 30% of all red diamonds have been discovered, leaving many curious to what showstoppers remain untouched below the surface.

The colour red is thought to symbolise love, passion and strength, which makes red diamonds an especially meaningful shade for collectors with significant funds. Those with an eye on the market will undoubtedly have spotted The Argyle Everglow - a 2.11 carat polished radiant-cut diamond presented as part of the 2017 Argyle Pink Diamonds Tender. 

Read more: The World's Most Expensive Diamond at Auction.

The Argyle Everglow was immediately identified for its miraculous size, colour and clarity and, after being assessed by the Gemological Institute of America (GIA), it has been given a grade of Fancy Red VS2.

Just to put the significance of this into perspective, in the 22-year history of the Argyle Pink Diamonds Tender, there have been less than 20 carats of fancy red certified diamonds sold.  

Argyle Everglow 2.11 carat radiant shaped Fancy Red. Image by Rio Tinto.

The 2017 Argyle Pink Diamonds Tender, also named 'Custodians of Rare Beauty' will present 58 diamonds with a total carat weight of 49.39 carats, including four fancy red diamonds, four purplish red diamonds, two violet diamonds, and one blue diamond.

The five 'hero' diamonds in the collection are as follows:

  • The Argyle Everglow, 2.11 carat radiant shaped fancy red diamond
  • The Argyle Isla, 1.14 carat radiant shaped fancy red diamond
  • The Argyle Avaline, 2.42 carat cushion shaped fancy purple-pink diamond
  • The Argyle Kalina, 1.50 carat oval shaped fancy deep pink diamond
  • Argyle Liberté, 0.91 carat radiant shaped fancy deep grey-violet diamond

 

Argyle Avaline 2.42 carat cushion shaped fancy purple pink. Image by Rio Tinto.

Read more: 'Diamonds: Rare Brilliance' Showcase Collection.

Found primarily in Australia, Africa and Brazil, red diamonds are so rare that only 20 to 30 stones are officially known to exist with each one measuring less than half a carat on average.

Argyle Liberte 0.91 carat radiant shaped fancy deep gray violet. Image by Rio Tinto.

Argyle Kalina 1.50 carat oval shaped fancy deep pink. Image by Rio Tinto.

In light of the reveal of The Argyle Everglow, we hit the archives to recall the most spectacular discoveries of red diamonds that have captured the interest of high-end jewellers, aficionados and collectors worldwide...

The Hancock Red Diamond

Whilst this round brilliant-cut diamond is not famous for its size, weighing in at 0.95ct, it is praised for its astounding deep red and purple colours, making it one of the most highly sought-after stones to date.

The Kazanjian Red

With a history nearly as big as its size, this South African diamond, although later cut in the Netherlands, was found over 100 years ago weighing in at 5.05 carats from the original rough 35ct stone. In 2010, the Kazanjian red diamond was on display in the Morgan Memorial Hall of Gems at the American Museum of Natural History before being purchased by Kazanjian Bros. Inc.

The Moussaieff Red Diamond

Discovered by a Brazilian farmer in the 1990s, the Moussaieff Red, otherwise known as 'Red Shield' is an internally flawless, triangular brilliant-cut fancy diamond famous for its 5.11 carat weight. This iconic diamond remains one of the largest red diamond discoveries in the world to date.

The Edcora Red

This pear-cut fancy red brown diamond, weighing in at 5.71 carats is known as the 'lost stone' due to vanishing from the public eye into the collection of a private investor. Whilst there have been no identified photographs of this red diamond, its existence has been well-documented in writing.

The DeYoung Red Diamond

The DeYoung red diamond is a rare 5.03 carat unmounted diamond purchased by a Boston jewellery seller at a flea market. Sydney DeYoung initially mistook the stone for a garnet but, upon noticing its high quality, had it laboratory tested to reveal its true identity as a red diamond. After his death in 1986, the DeYoung red diamond was given to the Smithsonian Institution’s Natural Gem and Mineral Collection where it remains on public display.   

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image 2017 Argyle Pink Diamonds Tender hero diamonds from Rio Tintos Argyle Diamond mine. ©Rio Tinto.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


Additional Info

Read more...

Investigating Ammolite with Canadian Mining Specialist Korite

Korite is at the forefront of ammolite mining and production, with plans now in place to expand its operation in Canada. Sarah Jordan speaks to the company's president, Jay Maull, to discover how a booming Chinese market, Feng Shui and adventurous jewellery designers are supporting this fascinating gemstone.

The buzzing, cosmopolitan city of Calgary, in Alberta, Canada, may be more famous for its skyscrapers and its role in Canada’s oil industry, but dig a little deeper and you will discover the city plays a unique role in the global gem industry.

This area of Canada – Southern Alberta’s Bearpaw Formation – produces more than 90% of the world’s ammolite; a gemstone composed of aragonite and derived from fossilised ammonite shells that are more than 70-million-years old. The company behind this production – Korite – is at the forefront of mining, producing, finishing and promoting ammolite across the world, with its jewellery and home décor items now available in more than 28 countries.


A complete ammonite fossil with the signature colourful ammolite shell.

Korite has been devoted to ammolite for 35-years and its efforts have certainly paid off. Earlier this year, it was announced that the company’s mining activities will expand by eight acres, taking total production up, by around two million carats, by the end of 2017. This shift has largely been caused by increased awareness of and demand for ammolite, which was only certified as an official gemstone by the World Jewellery Confederation (CIBJO) in 1981. Its vibrant, colourful appearance and reputation as nature’s rare ‘sleeping beauty’ has all added to its unusual mystique.

Korite president Jay Maull explains: “We believe we are just on the tip of ammolite going mainstream, both in terms of jewellery and home décor. We are in discussions with several major jewellery companies to carry our products and our gemstones in their products. We are concentrating on the United States. Ammolite is being fast-tracked because of modern day communications and the internet – we can be all over the world with the product.”

What is Ammolite?

Ammolite is derived from the fossilised shells of ammonoids – an extinct group of marine mollusc cephalopods that are closely related to today’s octopuses, squid and cuttlefish. Ammonite fossils are relatively common; the name derives from their tell-tale textured spiral shape, which reminded the Ancient Greeks of the Egyptian ram-horned god, Ammon.

Despite this common occurrence, only the rarest of these fossils exhibit the preserved shell required to make ammolite gemstones. As Maull explains: “Ammonite fossils are found all over the world. It was a very prolific creature that lived for around 300 million years across the globe. In every other place where they are found the shell has been destroyed by time and not preserved. Or, if it has been preserved, it is a reddish-brown and not suitable for making gemstones. The only place in the world that we have found the shell preserved is a small pocket in Alberta.”

What caused this unique preservation is not fully understood. Maull cites “many theories” including the presence of volcanic ash over the millennia. He adds: “We do find a lot of bentonite [absorbent aluminium phyllosilicate clay usually the presence of water] in the sediment, so there was a lot of volcanic activity in the area as it was forming and that may have preserved the shell. It really is an ongoing mystery.”


Inlay ring made from ammolite.

Despite this, there is still plenty we do know about ammolite. Korite deals in four grades of jewellery-appropriate ammolite gemstones: AAA, AA, A and standard. The AAA grading refers to the broadest range of colour, vibrancy and quality, with rarer stones blending blue, indigo and violet shades with the more common red and green hues. For comparison purposes, AAA is deemed similar in quality and rarity to D-flawless diamonds.

As the ammonite shells are in a delicate, preserved state, getting them out the ground is no easy task. “It is the same as any other strip mining operation, until we get down to the pay zone,” Maull explains. “We have to move the sediment very carefully because ammonites are fragile. When we do find one, all the heavy equipment stops and it becomes a hand process. There is a palaeontological aspect to it, and we have to teach our miners how to remove it without damaging it — this is a process we have perfected.”

Ammolite and Feng Shui

With such vibrant colours, it is understandable that finished ammolite jewellery and ammonite fossil specimens are growing in popularity, especially in the Asian market. Feng Shui experts believe that ammolite has absorbed a substantial amount of the earth’s positive energies, also known as qi (ch-ee). One form of this is light energy, which is evident in the multitude of colours in ammolite.

According to Feng Shui, our brain interprets light energy as colour, so these colours and their specific wavelengths can be used to balance our lives. Ammolite is recognised as the ‘Seven Colour Prosperity Stone’ due to its seven distinct colours; red is said to nourish love, orange promotes creativity, yellow improves wealth, green improves wisdom, blue aids health, indigo encourages peace, and violet stimulates growth and energy.

For Feng Shui masters, ammonite fossils are also special for their spiral shape, mimicking the path the universe’s forces follow in space and nature. When shape and colour combine in phenomenal ammonite fossils, these natural treasures are coveted as luxury home décor objects.


Living room interiors displaying Feng Shui with an ammolite fossil in matrix.

Maull comments: “We have been doing business with a Feng Shui master in Hong Kong for 16 years, and there is no doubt that [Feng Shui and Korite’s expansion] are linked. This is also how our growth in China came about. We just struck a deal with a large jewellery company in mainland China and their demand means we have to expand the mine to accommodate.”

The Future of Ammolite 

Ammolite may be a ‘fringe’ gemstone right now, but, according to Korite, its value has increased by 300% over the past decade alone. Consumer awareness and education, especially in western markets, will be crucial in developing the reputation of ammolite in the coming years.

Retailers will also need the right knowledge to help their customers make informed decisions. For example, like pearls, ammolite reacts to acids, hairsprays and perfumes and should be stored separately from other jewellery to prevent scratching. Similar caution should be taken with ultrasonic cleaners and immersion in water.

“There are several things we market about ammolite,” Maull explains, “it’s rare, it’s precious and it’s exotic. It is the rarest gemstone in the world and everywhere we go [people say] they have never seen anything like it.” He continues: “It is very exciting, every day that we find ammolite it is like a new day, everyone loves finding it and we love working with it and taking it all over the world and showing it to people. It is very rewarding.”


Ammolite in matrix.

 

Impact of Ammolite Mining 

Korite places great emphasis on environmental and ethical concerns. For example, layers of soil are replaced in the order they were removed and native grasses are replanted. “The mainstay of our business is to respect the land and return it to its normal state, if we look after the land it looks after us. It has become the core of our company to extract the ammolite and leave the land as we found it. We are very proud of this, we have won environmental awards from the government of Canada, and our stewardship of the land is one of our highest priorities,” Maull notes.

Since 1983, Korite has established itself as the market leading name in ammolite. Its determination to put the gemstone, and Alberta, on the gemmological map is clearly just one facet of its global ambition. With finished jewellery and stand-out specimens supported by an enviable lore, it is clear that ammolite has branded potential. This is certainly good news for Korite, especially as it expects to be mining for another 50 years. ■

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image Pieces of rough ammolite. Image courtesy of Korite.

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Turkish Designer Özlem Tuna Named Gem-A’s Gem Empathy Award Winner at IJL 2017

Gem-A is excited to announce that Turkish jewellery designer and International Jewellery London (IJL) Design Gallery exhibitor, Özlem Tuna, has won the 2017 Gem Empathy Award with her 'Dance of Branches' ring.

This year, IJL exhibitors from across the globe were tasked with creating a hand-drawn or CAD rendered design based around a beautiful, fancy-cut gemstone sourced from award-winning gem-cutter, John Dyer.

Finalists in the 2017 Gem Empathy design competition in partnership with International Jewellery London 

The Gem Empathy judging panel, made up of Gem-A CEO Alan Hart, IJL Event Director, Sam Willoughby, Gem-A Chairman Maggie Campbell Pedersen, and guest judge Liza Urla of jewellery platform GEMOLOGUE, was tasked with selecting a design that uses the 4.14 carat zig-zag green tourmaline in the most innovative and captivating way.

Despite stiff competition from a number of emerging designer-makers and brands, Özlem Tuna of Özlem Tuna Design was unanimously selected as the winner of the competition for her 'Dance of Branches' ring.

The sculptural piece was inspired by nature and features two curved bands in either 18k green or white gold, designed to look like the branches of trees moving in the wind. These bands of gold meet at the green tourmaline gemstone, which appears to float above the surface of the precious metal like leaves on a tree.

Dance of Branches ring by Özlem Tuna

Judges praised the design for its architectural, yet fluid shape and the prominence afforded to John Dyer’s striking fancy-cut gemstone.

Gem-A CEO Alan Hart commented: "I was instantly attracted to Özlem Tuna’s design, which not only showcases John Dyer’s eye-catching zig-zag cut tourmaline to great effect, but also offers a contemporary, sculptural aesthetic reminiscent of a work of art. We are pleased to continue the tradition of Gem-A’s Gem Empathy Award at IJL, and we look forward to seeing the ‘Dance of Branches’ ring come to life very soon."

Özlem Tuna Design advocates sustainable design and cultural preservation through its contemporary jewellery and homeware collections, which have been designed, produced and sold in the Historical Peninsula area of Istanbul since 2003.John Dyer's zig-zag cut tourmaline, presented to Özlem Tuna Design at IJL 2017

Commenting upon the winning design, Brand Manager at Özlem Tuna Design, Fatos Burcoglu said: "It is my honour to work with a Turkish jewellery design who has now won the 2017 Gem Empathy Award. This accolade highlights the success of Turkish designers. Now, our aim is to continue to showcase the existence of Turkish designers across the world and encourage their proliferation and success."

The Özlem Tuna Design team was presented with the 2017 Gem Empathy Award and the striking green tourmaline gemstone at IJL on Tuesday, September 5. The brand will now bring its winning design to life and the final piece will be unveiled at a future Gem-A event.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership

Main image from L-R: IJL marketing manager, Leigh Martinez, Gem-A CEO, Alan Hart and Gem Empathy Award winner, Özlem Tuna. 


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

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Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

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Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

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Birthstone Guide: Tourmaline for Those Born in October

Julia Griffith FGA DGA EG, looks at tourmaline, the enchanting rainbow-coloured birthstone for October.

Tourmaline is the rainbow jewel of the gem world. No other gem is available in such an impressive array of colours. Paired with good durability and high lustre, this gemstone has become a favourite of many.

Tourmaline Colours 

The hues, tones and saturations of tourmaline seem limitless, ranging from soft shades to vibrant explosions of colour. The desirability of the colour has a huge impact on price. The more vivid, rarer colours reach higher values, such as the coveted electric-blue copper bearing Paraiba tourmaline.

Read more: Gem-A confirms oldest known carved tourmaline

Many tourmalines have commercial names such as rubellite for pink to red tourmaline. It is also common to describe them simply with the pre-fix of their colour i.e., 'pink tourmaline'.

Parti-Colour Tourmalines 

Tourmaline is also known for its colour-zoned or "parti-coloured" specimens, where different zones of colour can be seen in the cross-section or down the length of the crystal. These can be cut to display the different colour patterns either as slices, creative carvings, facetted or cabochon gemstones, or left as whole crystal specimens. The most popular colour-duo is watermelon tourmaline which display pink on the inside and a rim of green on the outside.


Bicoloured tourmaline on quartz. Image: ©Gem-A

Tourmaline is a complex boro-silicate of aluminium, magnesium and iron and the vast selection of colours are due to trace impurities and colour centres. The availability of these impurities may vary during growth, which allows for the development of different layers of colour.

Read more: Getting to grips with multi-colour gemstones

Its chemical makeup is so complicated that it cannot be synthesized, and is therefore always of natural origin.

Tourmaline Crystals 

The crystals are easy to identify with the tell-tale rounded 3-sided, or 6-sided, cross sections. They are often long and prismatic with heavy striations down the length of the crystal and are topped with either a pyramid or a flat pinacoid.


Watermelon tourmaline. Image by Pat Daly. ©Gem-A

Tourmaline Discovery 

First discoveries have been attributed to both Brazil and Italy in the 1500's. The name of tourmaline was derived from the Sinhalese phrase tura mali, which was used by the miners and traders to refer to "unknown stones of mixed colours". The advancement of mineralogy allowed the recognition of tourmaline as its own gem species in the 1800's.

Tourmaline Mythology

Since their discovery, tourmalines have been used as talismans for protection against toxins and radiation as well as many other healing properties which are associated with particular colours of tourmaline. They are said to emit far-infrared rays that penetrate the body and stimulate and soothe the tissue within.

This association is likely linked to the ability of tourmalines to become charged when heated, which is known as pyroelectricity.This property causes tourmalines to readily attract dust, and so a regular flick with a duster is recommended if they are displayed under hot lighting - arguably, a small inconvenience for such a stunner of a gem.

Facts about Tourmaline 

Tourmaline has a hardness of 7 - 7.5 and good toughness, making it suitable for use in jewellery. Inclusions are fairly common in tourmaline and many contain mirror-like fractures within them, which can be quite attractive, but may compromise the durability if knocked. Inclusion free stones are available and will fetch a premium price.

Parallel needle-like cavities are also common in tourmaline, which in vast numbers can create chatoyancy, or the "catseye", effect.

This article was written by Julia Griffith, FGA DGA EG at Gem-A for the Oct/Nov 2017 issue of The Jeweller - The magazine of the National Association of Jewellers

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image Tourmaline group. Image courtesy of Julia Griffith.

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Graff Diamonds buys 1,109ct Lesedi La Rona Diamond for $53m

The second largest gem-quality diamond ever discovered has been sold privately to Graff Diamonds for a staggering $53 million. 

First unearthed by the Lucara Diamond Corporation in the Karowe mine in Botswana, the Type IIa Lesedi La Rona diamond weighs in at 1,109 carats. It was initially put up for auction in June 2016, but after failing to reach its pre-sale estimate of $70m, stalling at $61m, the diamond was hidden away. 

Graff has a long-running reputation for buying big diamonds, including a 373 carat rough believed to be a fragment of the Lesedi La Rona in May 2017. The price was a cool $17.5m. 

Read more: Magnificent 51ct Dynasty Diamond Unveiled by Russian Mining Giant

The Karowe mine is also where the 813 carat Constellation diamond was uncovered in 2015. This particular diamond holds the record as being the world's most expensive, having been sold for $63m to a Dubai-based company. It is now in the hands of de Grisogono founder, Fawaz Gruosi, who is transforming the rough into as-yet-undisclosed masterpieces. 


Whilst the Lesedi La Rona diamond failed to sell at auction, it has now been privately sold to Graff Diamonds for $53m. ©Graff Diamonds


The 1,109-carat Lesedi La Rona is the second largest diamond in the world. ©2017 Lucara Diamond Corp.

Commenting on the purchase, Graff Diamonds founder and chairman, Laurence Graff, commented: "We are thrilled and honoured to become the new custodians of this incredible diamond. The stone will tell us its story, it will dictate how it wants to be cut, and we will take the upmost care to respect its exceptional properties. This is a momentous day in my career, and I am privileged to be given the opportunity to honour the magnificent natural beauty of Lesedi La Rona."

Lucara president and CEO, William Lamb, called the discovery of the stone a "company-defining event". He noted: "We took our time to find a buyer who would take the diamond through its next stage of evolution. Graff Diamonds is now the owner of the Lesedi La Rona as well as the 373-carat diamond... We are excited to follow these diamonds through the next stage of their journey."

High jewellery aficionados will now have to wait patiently to see what Graff Diamonds does with this incredible rough. 

Read more: Extraordinary emerald valued at $309 million is unearthed in Brazil

For further information and photos of the Lesedi La Rona visit lucaradiamond.com
Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.
If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image: The 1,109-carat Lesedi La Rona diamond sold to Graff Diamonds. ©2017 Lucara Diamond Corp.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


 

Additional Info

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Birthstone Guide: Topaz for Those Born in November

Gem-A gemmology tutor Lily Faber FGA DGA EG takes a closer look at topaz, the birthstone of November, and explains why this gem should be high up on your Christmas wish list.

For those born in the cold month of November, topaz is a well-known and hopefully well-loved gemstone. For those born during the rest of the year, you may want to steal this birthstone for yourself!

Topaz History and Meanings

The name topaz most likely originated from the Sanskrit word 'tapas', meaning 'fire'. This gemstone is thought to promote creativity, increase sensitivity to taste to enhance your dining experiences, boost mental clarity and to uncover lies and illusions.

The ancient Greeks believed that topaz could render the wearer invisible - though I have yet to see proof of this effect! Topaz is the state stone for Texas and Utah in the United States of America and is the talisman for the astrological sign Sagittarius.


Blue topaz with incipient cleavage seen under table. Photo courtesy of Lily Faber, Gem-A.

Topaz Colours and Localities

Topaz is most often associated with the colours yellow, orange, blue or pink, but it can also be colourless, green and brown. Topaz comes in some of the gem world’s largest crystals that have to be measured in kilograms and not carats. A famous example is a single transparent topaz crystal from Minas Gerais, Brazil, which weighed 596 pounds.

Read more: Why Are Some Gemstones Associated with Bad Luck?

One of the most valued colours is known as 'Imperial Topaz', which is pinkish-orange to red-orange. Another highly valued colour is 'sherry topaz', which is brownish-yellow to orange or yellow-brown.

What about Imperial Topaz?

Topaz can be found in Brazil, Russia, Pakistan, Mexico, the USA, Madagascar and Sri Lanka. In the 19th century, the main source for pink topaz was in the Ural Mountains in Russia. The imperial family, including the tsars, reserved exclusive rights to own and wear the colour, thus imparting the name 'Imperial topaz'. It is less common than other naturally occurring colours of topaz and is thought to resemble the colours of the setting sun.

Topaz Crystal 7316 PDRed-orange and pink tones in a single topaz crystal. Photograph by Pat Daly, Gem-A. 

Historically, all yellow stones were called topaz, which has since been corrected, for the most part. In some shops, misnomers can still be seen today. Misleading names like 'quartz topaz', 'Scotch topaz' or 'Spanish topaz' are used for citrine quartz, so don't fall for it!

Topaz Colour Treatments

It should be noted that almost all pink topaz on the market today is mined in Brazil and heat-treated to bring out the pink colour. Natural blue topaz is typically pale, and stronger colours like 'London blue' or 'Swiss blue' are achieved by irradiating and heating a colourless topaz to promote and stabilize the blue colour.

One colour that was not created by nature is known as 'mystic' topaz. It is a colourless topaz that has been coated with a thin metallic layer to produce extreme iridescence.

Topaz Properties

Topaz is a relatively hard material, with a level of 8 on the Mohs scale of hardness. While it can take a high polish and show a bright vitreous lustre, its perfect and easy cleavage lets it down. Cleavage is a directional breakage that occurs along a crystal plane in only crystalline materials. 

Read more: Exploring the Varieties of Quartz

Topaz has what is called 'basal' cleavage, which is 90 degrees to the direction of crystal growth, or the c-axis. This breakage leaves a flat base (basal pinacoid) with the tell-tale terrace-like markings that look like tiny, wavy rivers running across the flat surface of the crystal. Any forceful knock or pressure can split the stone in two along this direction, so great care is taken when fashioning these stones. If wearing topaz set in a ring, it would be advisable to wear it in a rub-over setting to protect as much of the stone as possible. Otherwise, simply wear it in a necklace, earrings or, if you are feeling very fancy, a tiara.

Other things to know about topaz is that it's pleochroic, meaning it displays different colours in different crystal directions.

Topaz Inclusions

Topaz crystals are typically transparent with multiple straight, parallel striations running down the length of the crystal and a pyramidal termination at the top. They have a rhombus-shaped cross-section which looks like an elongated kite-shape.

Read more: What Career Paths Can Trained Gemmologists Take?

Inclusions can consist of healed internal fractures (feathers), long tube-like cavities and two-phase inclusions or a cavity with two immiscible liquids. Iridescence can be seen in both rough crystals and cut stones where there are internal fractures, or where cleavage is just starting to extend into the stone from the surface (also known as incipient cleavage). Also seen are variously coloured mineral inclusions.


Top: Striated topaz crystal with iridescence due to internal fractures. Bottom: Iridescence within incipient cleavage. Photos courtesy of Lily Faber, Gem-A.

If you've never thought about topaz jewellery, now's the time to add this colourful gemstone to your collection. London blue topaz especially is growing in popularity, with many jewellery lovers choosing this gemstone instead of aquamarine and sapphire for statement cocktail jewellery. 

Read more: What Should Be in the Ideal Gemmologist’s Toolkit?

Those born in November are lucky enough to have two beautiful gemstones as their birthstones. Find out more about citrine, a variety of quartz, here.

Learn more about gemmology with our Short Courses and Workshops.

Start your gemmology education no matter where you are in the world with our Online Distance Learning

Cover image: A trio of faceted topaz photographed by Pat Daly, Gem-A. 

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Andrew Cody Awarded Honorary FGA at Gem-A Conference 2017

Gem-A is thrilled to announce that Andrew Cody, founder of leading Australian opal company, Cody Opal, has been awarded an honorary FGA in recognition of his exceptional services to gemmology and the wider industry.

Cody was named the recipient of this special recognition at the annual Gem-A Conference 2017, which took place from November 4-5 in London. His achievements were honoured by Gem-A CEO Alan Hart, before he was invited on stage to accept and share his thoughts with Conference visitors and delegates.

Cody started collecting fossils, minerals and gemstones at just 12 years of age. He began cutting opal in 1964 after a school excursion to Coober Pedy, in northern South Australia, more than 800km north of Adelaide. In 1971, he established a wholesale opal and gem-cutting business, which expanded to include exporting to Europe, Japan and the United States.

Read more: Gem-A Conference Speaker in the Spotlight - Q&A with Adonia Pouroulis 

During his professional career, Cody has played a key role in transforming the reputation of opal as Australia’s National Gemstone. This included the production of an award-winning opal stamp series with Australia Post, the design of the official National Gemstone emblem and development of the official 'Opal Nomenclature'.

Cody is also a successful author, having written 'Australian Precious Opal – a Guide Book for Professionals'. In 2010, Cody and his brother Damian published a second book, 'The Opal Story', which is now available in six languages with more than 50,000 copies in circulation.

Cody is the joint founder and director of The National Opal Collection (NOC) with showrooms and museums in both Sydney and Melbourne. His opalised fossil collection is particularly impressive, and includes a 2.5 metre opalised pilosaur, and the opalised upper jaw of a rare Mesozoic mammal. This passion for collecting is accompanied by a strong business sense, leading to both of Cody’s businesses being awarded Government Export and Tourism Industry accolades. Additionally, he has a Gold Commendation from the Lord Mayor of Melbourne, is an honorary fellow of the Gemmological Association of Australia and is a research associate of The Australian Museum.

Read more: Gem-A Conference Speaker in the Spotlight - Q&A with Patrick Dreher

His commitment to the industry has seen Cody take on a number of official positions, including president of the Australian Gem Industry, founding member and chairman of the Australian Jewellery and Gemstone Industry Council, and president of the International Colored Gemstone Association.

Most recently, Cody has been working with a number of organisations on a review of opal classification. His goal is to create a universal system throughout the world gemstone community. In order to achieve this goal, he has put together 50 master reference sets for use in education and laboratories. These comprehensive sets contain 215 opal specimens in each.

When he’s not championing opals, writing, sourcing or working in the trade, Cody enjoys sharing his 50-year passion for opals at regular speaking engagements.

Cody commented: "When I was told of the nomination, I was overwhelmed and in fact I still am. I never considered myself deserving of this honour, and feel there would be many more that are better qualified! But it is with gratitude that I accept this important award from the world’s oldest gemmological institution.

Read more: Gem-A Conference Speaker in the Spotlight - Q&A with Samanta & Vladyslav Yavorskyy

"I am fortunate that my early interest in rocks and fossils grew into a hobby that also earned me a living throughout my life. It was about discovering treasure buried in the earth, outback adventures, travel and basically having fun. I loved being my own boss and, after all, who would employ me? So after all these years, I am still pursuing my hobby!

"The opal gemstone is amazing in that is has links to many areas of science; this has led to my collection of opalised fossils, pseudomorphs and related opal specimens from around the world."

He concludes with a spark of humour: "I don’t suppose you know anyone who wants to sell me a meteorite with opal, do you? I wonder if one day they will find evidence of bacteria preserved in opal on Mars?"

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image courtesy of Andrew Cody


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


 

Additional Info

Read more...

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite).

It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special

Read more: Zircon from Vietnam

Admired since ancient times, turquoise is known for its beautifully unique colour, ranging from powdery blue to an unrivalled 'robin's egg' blue. Its colour and historic significance have resulted in turquoise becoming a favourite of many.


Displaying the different properties of turquoise: cut, clarity, colour and carat weight. Photos ©Gem-A

Gemmology of Turquoise

Gem turquoise is a polycrystalline copper material typically occurring in thin seams or small nodules. Turquoise is found in dry, barren, arid regions where copper, leached from rocks by rainwater, reacts with aluminium and phosphorus.

The result of this reaction is a porous, semi-translucent to opaque compound of hydrous copper aluminium phosphate with some evidence of iron. Copper produces the blue hues whilst chrome and iron add tonal variations of green.

Read more: Natural Vs Enhanced Lapidary Materials

Quite often, small patches or veins of brown or black host rock, known as matrix can be seen in the stone. The presence of these 'spider-web' patterns can often lower the value of the stone. However, some buyers actively seek stones with a presence of its matrix as they can be more unusual and attractive.


Turquoise simulant; paste. Photo courtesy of Pat Daly.

In terms of market-value, turquoise stones completely free from traces of matrix command a higher value, whilst those with evident spider-web patterns classified as desirable fetch second-place value in the trade.

The History of Turquoise

The earliest evidence we have of this gemstone dates to 3,000 BCE, under the reign of King Tutankhamun. The oldest turquoise mines are believed to have been located in the Sinai Peninsula of Egypt. Elaborate displays of turquoise were found on the gold jewellery of many Egyptian pharaohs, with the most extravagant found set on the iconic burial mask of King Tut himself.

Read more: Exploring the Varieties of Quartz

Ancient Persians believed that turquoise guaranteed protection. They adorned many of their palace domes with the sky-blue gemstone as it was said to represent heaven. Additionally, ancient Persians often engraved Arabic script into turquoise which would then be used to intricately decorate their daggers and horses' bridles.

Read more: Gem-A Confirms Oldest Known Carved Tourmaline

The highly prized 'robin's egg' blue - also known as 'Persian turquoise' - was venerated by the people of Persia (now known as Iran) as well as Siberia, Tibet, Turkey and Afghanistan. It was Turkish traders who later introduced this 'Persian blue' stone to Europe in the 13th century through the Silk Road.

Map of localities where turquoise is found throughout the world.

Archaeological evidence shows that not only was this gemstone used to embellish ancient Egyptian ornaments but was also a primary carving material for Chinese artisans. For many Native Americans, turquoise held great ceremonial value in being an instrument of exchange between tribes.

Read more: Understanding Red Beryl

As the national stone of Tibet, turquoise is enriched with ancient lore of being a symbol of good health, fortune and success. Often referred to as a token of protection, turquoise was commonly worn to ward off the presence of evil spirits, granting its wearer a sense of power.

Properties of Turquoise

The texture of turquoise is a direct result of its composition and structure. As an aggregate, polished turquoise with a smooth waxy lustre has a tightly-packed crystal structure, low porosity and a fine texture.

Read more: Getting to Grips with Multi-Tonal Gemstones

Turquoise gems displaying a dull lustre when polished have a coarser texture and increased porosity due to a less-dense internal crystal structure. This range in texture and porosity not only directly affects the overall appearance and lustre of this gemstone but also influences its durability.

Typically, turquoise is a fairly soft stone which made it a popular choice for talisman carving across ancient history. Throughout America, many carvers fashioned turquoise into amulets of Native American significance such as birds and animals.

Turquoise Jewellery Designs

With a hardness of 5 ½ - 6 on the Mohs scale and a fairly good toughness, turquoise is a suitable material for use of jewellery. However, the toughness of turquoise is significantly less in stones of a coarser texture.

This December birthstone is sensitive to direct sunlight and natural solvents such as perfume, oils and makeup products.

Read more: What Gemstones Are in the Beryl Family?

Due to its porosity, turquoise that is polished and faceted for commercial jewellery is often treated with paraffin compounds in order to increase its durability by oiling or waxing the surface of the stone.


Turquoise simulant; Dye-treated magnesite. Photo courtesy of Pat Daly.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's Short Courses or Workshops. If you’re ready to get started, learn more about the Gemmology Foundation course.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image: Surface patterns and textures of different cabochons of turquoise. All photos courtesy of Pat Daly at Gem-A.

Additional Info

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Greenland Ruby: The Mighty Aappaluttoq Arises

With an opulent supply of rubies and pink sapphires, mining company Greenland Ruby is set to become an influential supplier of coloured gemstones. Here, International Women in Mining board member, Deborah Craig FGA DGA, shares her experiences in Greenland.

Greenlanders call the buried treasure of blood red rubies and vivid pink sapphires Aappaluttoq or "Big Red". Mining has now begun, positioning Greenland Ruby to become one of the market's most important suppliers of coloured gemstones. The rubies and sapphires will have an ethical pedigree that is increasingly important to buyers: responsibly-mined, with a transparent chain of custody and fully-disclosed treatments.

The new mine is also important to the people of Greenland, who voted for self-rule in 2008 with increased independence from Denmark. This means taking control of the development of their mineral resources and diversifying the economy from fishing and tourism, while creating self-sustaining tax revenues. Aappaluttoq is one of the first new industrial mines to come on-stream since this change went into effect.

Aappaluttoq is nestled between sea and glacier, 150 km south of the capital Nuuk, and east of the fishing village of Qeqertarsuatsiaat. The hilly, barren land is impassable, accessed only by small boat or helicopter (1). Geologists discovered significant ruby mineralisation in 2005; years of systematic exploration revealed the Fiskenaesset Anorthosite Complex. The metamorphic rocks that host the mineralisation are thought to be 2.9 billion years old, making Aappaluttoq one of the oldest coloured gemstone deposits worldwide.


1. The author and Jens Frederiksen, VP Security & Sales, Greenland Ruby. Helicopters are needed to reach the remote mine site.

A positive prefeasibility study was completed in 2011, after sufficient drilling and resource modelling. The ore is estimated to contain 10% corundum, of which 5% is gem quality, 20% near-gem quality (i.e. with inclusions), and 75% is commercial grade. The mine's profitability will depend on maintaining these robust grades, as well as efficiently extracting the gemstones from the ore.

Larger stones are found in the deposit, but their recovery is variable and difficult to predict. Therefore, only melee-sized rough material (<4mm) was included in the study and will underpin the steady sale of gemstones to the market. In this way, an industrial mine can provide a reliable supply of stones to jewellery manufacturers, something small alluvial operators cannot do.

Construction began in 2015 at a capital cost of US$25 million. Last fall, LNS Norway, parent company of Greenland Ruby, acquired the mine when previous owner True North Gems struggled to provide sufficient funding. LNS Norway has developed other projects in remote Polar Regions, including Antarctica and Svalbard. The mine is currently expected to operate for 9 years and produce 87 million carats of rough gemstones. Greenland Ruby is mapping and sampling its nearby Siggartartulik and Kigutilik projects, hoping to expand the mine's resource base.

The mine site will operate year-round and is staffed by Greenlanders flown to the camp for 2-3 week shifts. When possible, mine supplies are sourced locally, including fresh catches from local fisherman and hunters.

Aappaluttoq is a primary, hard rock deposit, containing two ore types: phlogopite hosts the higher chromium ruby, and leucogabbro hosts the pink sapphire (2). The ore is excavated from the open pit, mixed with lake water, and sent via conveyor belt on its circuitous route through the processing plant (3).


2. Aappaluttoq ruby in host rock.

A primary crusher reduces the size of the ore to below +60mm; a cone crusher reduces it further to below +20mm. After being washed, the crushed ore is mixed with a ferro-silicon solution (SG 2.7) in the dense media separation circuit and spun in a DMS cyclone. The heavy corundum sinks, and the lighter, floating waste material is diverted to tailings.

The corundum is separated into three size categories, before passing through a dry magnetic separator and an optical sorter. The optical sorter uses white light, a series of cameras, and a computer to identify red and pink crystals, triggering a pulse of pressurised air that separates the coloured material from the feed. The rough ruby and pink sapphire is transported from the processing plant to Nuuk, where any residual host rock is removed with hydrofluoric acid.


3. Aappaluttoq ore processing facility.

Greenland Ruby is currently calibrating its recovery process to reduce the amount of waste rock that makes its way through the system. This includes adjusting the conveyor belt speed so the optical sorter can work more effectively, and tweaking the hydrofluoric acid concentration and soak times.

The cleaned gemstones are sorted in Nuuk (4), against a customised master set of stones. First, the stones are divided into gem and near-gem qualities. Each of these qualities is then divided into four colour categories, ranging from deep red to intense pink to light lilac pink (5,6 & 7).


4. Holly Noahsen of Greenland Ruby sorts gemstones at the Nuuk office.

As noted by Christopher P. Smith, Andrew J. Fagan and Bryan Clark Craig in their article 'Ruby and Pink Sapphire from Aappaluttoq, Greenland' (The Journal of Gemmology, Volume 35/ No.4, 2016, pp.294-306), the stones have metamorphic-metasomatic type rubies and sapphires from other world deposits, including Montepuez.

They exhibit moderate to strong dichroism, have no visible colour-zoning, are are relatively high in chromium and iron and low in titanium, vanadium and gallium. Inclusions include clouds of minute rutile particles and some fine rutile needles, as well as arrowhead-shaped platelets.


Top left (5). Aappaluttoq ruby in matrix. Top right (6). Ruby crystal with triangular growth marks. Bottom (7). The sorters separate the stones by colour and clarity using a customised master set.

As Aappaluttoq is a primary deposit, the gemstones have been subjected to intense pressure and are most likely fractured. Removing the stones from their host rock is also difficult. This means that the majority of stones will need to be treated to improve their transparency, a process that also reduces their purple undertone. Treatments will be fully disclosed and the chain of custody will be carefully tracked. At present, Greenland Ruby will sell the treated rough material; the feasibility of bringing lapidary in-house is being examined.

Greenland Ruby has begun a soft launch of their rough rubies and sapphires. The company believes their strength lies in their ability to provide a steady supply of quality gemstones to jewellery manufacturers. Greenland Ruby is also considering strategic partnerships with select jewellery houses, to collaborate on marketing campaigns that will highlight the extraordinary provenance of Greenland rubies.

And the Greenland government and Greenland Ruby have the opportunity to develop an origin certification scheme, like the one that made Canadian diamonds a success story in a market increasingly looking for ethical sourcing alternatives.

Closer Insight

All that is red is not ruby on Greenland (8) - tugtupite, Greenlandic for "reindeer blood", is a silicate closely related to sodalite. Tugtupite is a much sought-after opaque to translucent, becoming redder in sunlight. Nuummite, meaning "from Nuuk", is a black opaque gemstone that exhibits iridescent flashes of colour due to its lamellar, fibrous structure (9).

8. Tugtupite in matrix: the gemstones becomes redder in sunlight.

Greenlandite (10) combines quartz and fuchsite to produce an opaque green stone that may be streaked with black schlieren or flecked with pyrite. Small scale miners extracting these stones have been supported by the Ministry of Mineral Resources with workshops on mining best practices, gemstone pricing and lapidary.


Left (9). Nuummite, only found near Nuuk. Right (10). Greenlandite with a schlieren vein.

The Ministry maintains an ongoing gemstone mapping project, compiling data from historical reports and noting when geologists and small-scale miners make interesting discoveries in the field.

Deborah Craig FGA DGA, would like to thank Greenland Ruby for sponsoring her field visit to Greenland.

All photos ©Deborah Craig, unless otherwise stated.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image: Iceberg in coastal waters. Image ©Deborah Craig


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


 

Additional Info

Read more...

Gold Fever in Arizona: Searching for Gold in the United States

With its legends of gold seekers and treasure hunters, Arizona is still drawing the gaze of gemmologists and history enthusiasts to this day. Gem sculptor Helen Serras-Herman FGA takes us on a journey to this 'gold fever' state.

Living in a state where gold in abundance had been discovered in the nineteenth and early twentieth centuries, it was only inevitable that I would, at some point, find myself amidst gold fever.

Some incredible specimens of gold in quartz, found in central and southern Arizona, are part of splendid collections at the Arizona-Sonora Desert Museum as well as the University of Arizona (UA) Mineral Museum in Tucson.

A short time ago I finished carving two beautiful specimens of gold in quartz from an undisclosed location in southern Arizona, a commission work for the 'Arizona Lapidary & Gem Rough' store in Tucson. Today's gold miners are as secretive about locations as were the old timers.


Left: The stunning gold specimen from the Huachuca Mountains in Cochise County is part of the splendid mineral collection at the Arizona-Sonora Desert Museum in Tucson. Middle: This beautifully formed gold specimen from the Vulture Mine resides in the Arizona-Sonara Desert Museum's mineral collection in Tucson. Right: This is one of two beautiful specimens of gold in quartz from an undisclosed location in southern Arizona that I just finished carving.

My husband and I recently visited the Superstition Mountains, the centre of many gold legends and treasure hunts. We brought back some great specimens of gold in quartz from the famous Black Queen Mine in Goldfield.

But how did Arizona become a 'gold fever' state? I looked to prominent Arizona historian Jim Turner, a retired professor, author, and friend for some historic perspective: "In the 1730s, Spanish prospectors worked deposits twenty miles north of the US-Mexico border in an area later called Oro Blanco (white gold) because silver in the ore gave it a whitish colour." Later, when miners (the '49ers as they are known) started coming back from California's gold rush in 1849, they came through Arizona and found placer gold and gold in quartz deposits. Placer gold, found in stream bed deposits, originates from ancient larger ore deposits, from which small gold flakes detach and roll downstream.


Two great specimens of gold in quartz from the Black Queen Mine in Goldfield mined several years ago.

The Superstition Mountains and Their Legends

The Superstition Mountains are located less than an hour's drive east of Phoenix, just past Apache Junction. It is an area of 160,000 acres of dangerous land filled with saguaros, gold legends and Apache curses, conquistador and Mexican miners' stories, Jesuits' hidden gold treasure legends, as well as over 250 mysterious deaths. Gold seekers and treasure hunters have been searching in vain for the mine that bore the legend of the Superstition Mountains, the Lost Dutchman Mine, named after Jacob Waltz, a German prospector known as the 'Dutchman'. It is believed that he found the richest gold mine in the world, possibly an old Spanish mine, but took the secret to his grave in 1891, leaving behind only some riddle clues.

The legend of the Lost Dutchman Mine still reels in treasure hunters, who follow those clues on old paper or stone maps that take them deep into the Superstition Wilderness, an areas of 242 square miles that are filled with steep canyons, rocky outcroppings, cacti and thick brush.

Among the many that have lost their lives searching there, are three treasure hunters from Salt Lake City, Utah, lost forever as recent as July of 2010. The dangers from the Apaches, who killed many in the region protecting their sacred land and igniting the legendary Apache curse, are now long over. However, the danger from the summer temperatures that soar well above 110 degrees, are real, and make it deadly to unprepared hikers.

Mineral prospecting has been banned since 1983 when the area became a national wilderness, yet every year many travellers hope that they will stumble across the fabled gold mine.


Left: The Superstition Mountain & Lost Dutchman Museum treasure maps. Right: Dutchman matchbox SM Museum. Rich gold in quartz ore, supposedly from the Lost Dutchman Mine.

Lost Dutchman Museum

For a safe way to learn about gold in Arizona, its mining history and legends, head to the Superstition Mountain & Lost Dutchman Museum. With a variety of exhibits that allow the visitor to see what the Old West was really like, the museum provides a wealth of information about the old gold mines of the area. With stunning displays of treasure maps and over 40 books about the legend of the lost gold, many of them out-of-print, you truly understand the power of the legends and the quest for gold. After looking at the book display, one is very thankful that he museum offers and extensive bookshop!

The Superstition Mountain

The Superstition Mountain & Lost Dutchman Museum is located on Hwy 88, the historic Apache Trail, now designated as Arizona's first historic road. The trail covers 47 miles from Apache Junction to Roosevelt Lake. The drive, at times very rough with steep grades, offers some fantastic views of the backside of the Superstition Mountains, as well as of the three lakes that dam the Salt River: Canyon Lake, Apache Lake and Roosevelt Lake.

Nobody else can describe the Apache Trail better than president Theodore Roosevelt, on his way in 1911 to the Roosevelt Dam dedication ceremony: "The Apache Trail combines the grandeur of the Alps, the glory of the Rockies, the magnificence of the Grand Canyon and then adds as indefinable something that none of the others have, to me, it is most awe-inspiring and most sublimely beautiful".

Goldfield Ghost Town and Mine

Following the Apache Trail north for only a short drive, you will reach Goldfield Ghost Town, which lies in the shadow of the legendary Superstition Mountains. This is a true 1890's boomtown that had 50 working mines in the district after rich high grade ore was found in the area in 1892.

The abandoned town was revived in 1988, and today you can ride a narrow gauge railroad that circles the town for a mile and a half, offering a narrated scenic ride of the historic buildings and the famous Black Queen, Bulldog and Mammoth Mines.


Guided tours of the Goldfield Mine take you underground to a reconstructed mine very close to the original, now flooded mine.

Exploring Goldfield History

At the Goldfield Historic Museum, in the heart of the ghost town, you can learn more about the first very rich gold strike in 1892 and the 4,000 miners that lived there for five rich years. There are 13 treasure maps on display, from the so-called old Spanish maps, to more recent ones. A wonderful little museum with very friendly staff eager to share their knowledge!

Guided tours of the Goldfield Mine take you underground to a reconstructed mine very close to the original, now flooded, mine. It is always worth listening to the well-versed guides on the history of the local mine, discover the gold mining equipment that was moved there from the original nearby mines, and learn more about the mining procedures.

The Vulture Gold Mine

The Dutchman, Jacob Waltz, also prospected in the Vulture Mine, and was employed there as a consultant. The mine is located northwest from Phoenix near the old historic town of Wickenburg, famous today for its Western flair. There, in 1863 Austrian immigrant Henry Wickenburg, discovered gold. Legend has it that he was trying to retrieve a vulture that he had shot, when he found the quartz outcropping. Although Wickenburg sold the mine after a few years, it became one of the most productive gold mines in the history of Arizona, producing gold worth more than 200 million dollars. The gold is embedded in the quartz ore, and requires hard rock mining. President Franklin Roosevelt closed the mine in 1942, during World War II. The miners left, believing they would return in 6 months, but the mine never re-opened.

The Vulture mine used to be open daily for self-guided tours when we last visited in 2011, but now it is accessible only via a two hour guided walking mine tour on Saturday morning 8:30-10:30am. It is a great place to visit and walk the trails that take you by the 'Glory Hole', the Blacksmith's Shop and the Main Shaft, the Assay Office, and the 80-Stamp Mill. At the Power Plant, which served as the Machine shop, time almost stood still. All the equipment is still there, just a bit dusty and rusty, waiting for miners. This is a rarely seen sight, eerie and awe-inspiring. All the tools are left in place, as if the workers are just out for lunch.


Goldfield as it is today.

Prospecting for Gold Today in Arizona

According to stats from Gold Maps OnlineTM their maps show currently 46,199 active gold claims and 364,629 abandoned claims in the state of Arizona on public lands.

A great resource for information about gold in Arizona is the 'Gold Prospecting' page of the Arizona Geological Survey's (AZGS) website.


Gold in quartz from the Black Queen Mine. This site was one of three major mines; along with the Bulldog and Mammoth Mine that made Goldfield famous in the 1890s.

Several associations in Arizona promote recreational gold planning and mining. Members of the Arizona Association of Gold Prospectors (AAGP) Phoenix Chapter usually go prospecting within one or two hours' drive from Phoenix, Mesa or Tucson. The Gold Prospectors Association of America (GPAA) is a national organization. With five chapters in Arizona, there are plenty of locations and options to follow your gold fever.

For a two hour gold panning adventure join Apache Trail Tours, an award-winning our company based in Goldfield Ghost Town offering guided tours from one to eight hours.

If by now, you are sweltering from gold fever, besides going prospecting with any of the local gold clubs or purchasing gold specimens, you can buy your own gold mine in Arizona. My husband is already checking his wallet!

Next time you visit Arizona, please take a trip to these wonderful historic sites, museums and mines; they will enhance your knowledge about the difficulties of gold hard rock mining, the thrill of placer gold panning, as well as the successes and failures of gold-seeking. You may be inspired to go gold prospecting, or simply enjoy all the legends disseminated for over a century.

Sources

For currently available claims, please visit: goldmapsonline.com/arizona-gold-map.html, azgs.az.gov/minerals_gold.shtml, arizonagoldprospectors.org, goldprospectors.org, apachetrailtours.com, goldrushexpeditions.com/state/arizona/.

All images courtesy of Helen Serras-Herman.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image Goldfield Ghost is an abandoned town, revived in 1988, filled with museums, shops, and an underground mine, all in authentic-looking buildings. Image ©Helen Serras-Herman.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


Additional Info

Read more...

The Source of Garnets Found at The Arikamedu Archaeological Site in South India

Guy Lalous ends the year with his final Journal Digest of 2017 by exploring the chemical and mineralogical characterization of garnets found at the Arikamedu archaeological site in South India and their linkage to the rough material sourced from the Garibpet Deposit, roughly located 640 km away in Telangana State, east of the city of Hyderabad, India.

What about silicates and nesosilicates?

The vast majority of the minerals that make up the rocks of Earth's crust are silicate minerals. These include minerals such as quartz, feldspar, mica, amphibole, pyroxene, olivine, and garnets. The building block of all of these minerals is the silica tetrahedron, a combination of four oxygen atoms and one silicon atom. Garnets are nesosilicates. This subclass includes all silicates where the (SiO4) tetrahedrons are unbounded to other tetrahedrons.

What about garnets?

Garnets are a set of closely related minerals that form a group, resulting in gemstones in almost every colour. All garnets have essentially the same crystal structure, but they vary in chemical composition and properties. Many garnets are chemical mixtures of two or more garnet species, they are found throughout the world in metamorphic, igneous and sedimentary rocks. They have been grouped according to their composition in two groups. The ones that contain A1 in the B position in the formula are widely called pyralspites and the ones with Ca in the A position are ugrandites. These names are derived from the first letters of the single minerals in these groups; pyrope, almandine and spessartine make up the pyralspite and uvarovite, grossular and andradite are the members of the ugrandite group.

Garnets are isotropic and figuring out how each one of them fits into the six main mineral species and their mixtures can be a serious challenge. The gemmologist will need an accurate refractive index, specific gravity and UV-VIS spectrum to come to the right conclusion.


Table of identification of the main garnet species.

What about Arikamedu?

Arikamedu has initially been portrayed as a Roman settlement. Modern theories describe Arikamedu as an important Indian trading centre and harbour, connecting the east coast of India with the western world from the 1st century BC to the 7th century AD. Arikamedu served as one of the main bead-producing localities in India. The unearthing of several thousand stone and glass beads during the archaeological excavations attests to this fact. The glass is rich in potassium oxide K2O (Harder 1993). Some of the beads collected are cobalt glass with following gemmological properties: R.I.=1.52 spot, gas bubbles, swirl marks and chalky fluorescence (Jayshree Panjikar, Pangem Testing Laboratory, Pune, India). Garnets were the second-most prevalent among the stone beads after the quartz variety. Bead production remained on-going in the region for centuries and was only abandoned in the early 17th century.

The current study presents for the first time a thorough chemical and mineralogical characterization of garnets found at the Arikamedu archaeological site in southern India, using high-quality major- and trace-element data in conjunction with detailed inclusion studies. The authors then demonstrate a remarkable correlation with recently mined garnets from Garibpet in Telangana State, India - approximately 640km away of 760km distant by road - as the source of origin.

The Kothagudem-Garibpet area is located in the Vinjamuru domain of the Khammam schist belt and consists of Paleoproterozoic moderate-grade (and partly migmatitized) metasediments and metavolcanics with minor mafic and granitic intrusives. The conspicuous Garibpet Hill is formed of garnet-kyanite-muscovite schist and is surrounded by biotite schist and gneiss.


These faceted garnet beads were collected by local farmers from the Arikamedu site. The samples constitute some of those studied for this report and measure ~4.55-5.5 mm in diameter. Photo by K. Schmetzer.

What about Electron Microprobe Analysis?

During electron microprobe analysis, a sample is bombarded with a beam of electrons. The interaction of the electron beam with the sample material results in formation of X-rays, which can be analysed by the microprobe. The wavelengths and energies of these X-rays provide information about the chemical elements present in the sample (qualitative analysis). When compared with reference materials, the measured x-ray intensities can be used to determine element concentrations (quantitative analysis).

What about a Ternary Diagram?

A ternary diagram is a triangle, with each of the three axes representing a composition, such as the one in this study: pyrope, almandine and spessartine + grossular. The proportions of the three compositions sum to 100%. The plot graphically depicts the ratios of the three variables in as positions in an equilateral triangle. It is used in physical chemistry, petrology, mineral and other physical sciences to show the compositions of systems composed of three species.

The great majority of analysed samples from Arikamedu (beads and fragments) and the rough stones from Garibpet proved to be garnets with a high almadine content. The compositional fields were in close proximity and overlapped to a large extent. Microprobe data revealed almandine in the range of 77-84 mol% with minor components of pyrope, spessartine and grossular. A ternary plot of the molecular percentages of the garnet end members pyrope and almandine and the sum of spessartine + grossular showed that the studied garnets plotted within a relatively small compositional range. This outcome was even clearer when only a small portion of the full ternary diagram was drawn with an extended scale.

(a). This ternary diagram shows the chemical composition of garnets from Arikamedy and Garibpet calculated for the molecular end-members pyrope, almandine and spessartine + gossular. The compositions plot in a concentrated area, except for two anomalous Arikamedu samples (blue and purple arrows) that fall outside the main compositional field, which are inferred to be from different sources. (b). An enlarged detail of the main compositional field for the Arikamedu and Garibpet garnets corresponds to the area defined by the grey triangle in the inset. Note the extensive overlap in the composition of garnets from Arikamedu and Garibpet.

The compositional ranges for the two localities were:

  • Arikamedu: 77.4-83.5% almandine, 10.2-14.2% pyrope, 0.9-5.3% spessartine, 0.9-2.5% grossular
  • Garibpet: 79.2-84.0% almandine, 9.6-12.0% pyrope, 1.1-5.9% spessartine, 0.6-2.1% grossular

How does LA-ICP-MS work?

The LA-ICP-MS analysis process can be thought of in two main parts: material sampling i.e. Laser Ablation (LA) and chemical analysis i.e. Inductively Coupled Plasma Mass Spectrometry (ICP-MS). A tiny, nearly invisible ablation put is caused by the laser, into the girdle of the gemstone. There will be minimal damage as the laser vaporises only a microscopic amount of the sample for analysis. It nebulizes the material and the aerosol produced is transferred in a gas stream to an ICP-MS for elemental and/or isotopic analysis. An ICP-MS combines a high-temperature Inductively Coupled Plasma (ICP) with a Mass Spectrometer (MS). The ICP is an ionisation source where the energy is supplied by electric currents, which ionises the atoms. These ions are then separated based on their mass-to-charge ration (m/Q) and detected by the MS.

What is LA-ICP-MS used for?

LA-ICP-MS is recognised as one of the most important spectrometric techniques and has been used in gemmology for quantitative chemical analysis. It provides data that can be used to create chemical fingerprint diagrams for geographical origin determination.

The compositional averages and the ranges demonstrated by LA-ICP-MS analyses were nearly identical for the Arikamedu and Garibpet garnets. A similar relationship was noted for lanthanide rare-earth elements. Several samples from Arikamedu and Garibpet also showed chemical zoning for some trace elements, such as Y, P and Zn. Considering in detail both trace and other elements, chemical zoning between core and rim was strong for Mn and significant for Ca, largely consistent with the results of microprobe analyses.

How can we classify solid inclusions?

Solid inclusions are divided into three categories, by time of entrapment: those formed before the host crystal, called protogenetic; solids which arise from the solution from which both they and the host originated, called syngenetic and those formed after the host crystal has finished its growth, epigenetic.

The proto - to syngenetic inclusions in the cores comprised, with decreasing abundance: apatite, quartz, ilmenite, rutile, monazite, zircon, graphite and fluid inclusions. At the core-rim boundary, a very characteristic layer of fibrous sillimanite bundles was observed. Isolated zircon, monazite and quartz crystals were also found occasionally in the rims. The garnets were often cut by brownish-yellowish fractures coated by various generations of goethite or other iron oxides-hydroxides.


Coarse acicular sillimanite needles were observed in a small number of the garnets from Arikamedu. Photomicrograph by H.A.Gilg.

The small differences observed in the average chemical compositions between the Arikamedu and Garibpet material can probably be explained by the fact that the Garibpet samples were collected from one secondary source within a large garnet-bearing area and, therefore, are not entirely representative of the Garibpet rough material used for bead production at Arikamedu.

This is a summary of an article that originally appeared in The Journal of Gemmology entitled 'The Linkage Between Garnets Found in India at the Arikamedu Archaeological Site and Their Source at the Garibpet Deposit’ by Karl Schmetzer, H. Albert Gilg, Ulrich Schüssler, Jayshree Panjikar, Thomas Calligaro and Patrick Périn 2017/Volume 35/ No. 7 pp. 598-627

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image: Faceted garnet bicones from Arikamedu were cut in half and polished for microprobe analysis. Two drill holes meet approximately in the centre of each sample. Photo by H.A.Gilg.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


 

Additional Info

Read more...

Discovering Agates on the Shores of Cornwall, England

Cally Oldershaw FGA DGA describes the thrill of finding agate on the shores of Cornwall and reveals how these subtly-toned gemstones are shaping her jewellery collections in collaboration with geologist and lapidarist, Ben Church.

With many more people choosing to stay in the UK for their 'staycations' rather than going abroad for the holidays, the numbers visiting popular tourist regions such as Cornwall is increasing.

Agates of Cornwall

Of the Cornish rocks and the many millions of pebbles on the beaches, only a few are true agates showing the characteristic banding that defines them. The process of looking for agates is simply to visit a beach and walk slowly, looking at as many pebbles as possible. Determining whether a pebble is an agate is more of a challenge, it takes time and experience to identify the agates and from those, the ones that will be best suited to be made into jewellery.


A selection of Cornish cabochons and slices from Cally's jewellery collections.

Time and location are also important. The best time to look for the agates is when the tide is going out, as the banding in the agates shows better when they are wet; searching the intertidal areas from the high tide 'strand line' is likely to be most successful. Some beaches yield more agates than others and this changes with the tides and the seasons as the amount of sand and pebbles on each beach fluctuates, sometimes daily, throughout the year. It took us almost two years of researching and visiting potential collecting sites to develop an effective method of finding Cornish agates.

What is Agate?

Agates are a type of quartz, the same family as colourless rock crystal, purple amethyst, grey to brownish-grey smoky quartz, black morion and yellow citrine crystals. Cornish agate consists of banded varieties of chalcedony and many occasionally include areas of crystalline amethyst, rock crystal or morion. Chalcedony is defined as microcrystalline or cryptocrystalline (hidden crystals) quartz, where crystals are too small to be seen without using a microscope.

No two agates are alike; each is formed over millions of years and has its own unique colours and patterns. Their distinctive colours include grey, cream, caramel, white, colourless chalcedony. Some pieces have translucent or transparent bands, where it is possible see through the agate.

Left: A model wearing a pendant made of Cornish agate. Right: A Sculptural piece approx. 10cm across with purple crystalline amethyst

The Cornish agate pebbles and polished pebbles have been used in crystal therapies. Named for their colours; the more vibrant poldark agate and Cornish caramel agate, are believed to help energise, while the cooler colour of Cornish grey agate and Cornish cream agate have a calming effect. A reddish coloured blush agate is particularly rare.

Cornish Agate Formation

Most agates have a volcanic origin, with the agate filling cavities or vesicles (small bubbles) within volcanic igneous rocks. Cornish agates formed about 240 million years ago and have a different origin. The characteristic granite landscape of the Southwest of England including Dartmoor, Exmoor, and Bodmin Moor, as well as the Scilly Isles, are all part of a large intrusion of igneous rock, which slowly cooled between 1.5 and 3 miles underground, causing fissures and cracks in the surrounding rocks (country rocks).

Cornish agates formed from got silica-rich fluids that filled these cracks and fissures called veins (like the veins within a leaf) within the country rocks, and then cooled and solidified to form vein agate.


Another selection of Cornish agate jewellery in a variety of colours.

The country rocks surrounding the granite were folded and faulted as the sea floor between Cornwall and Europe was compressed, and the rocks buckled up to form the landscapes and coastal cliffs of Cornwall. Over millions of years, these folded and faulted rocks were weathered and eroded. In rare cases, the veins can be seen in the rock faces and cliffs at the back of beaches. As the rock was broken down, agates were released to the beaches, where the energy of the seas moved the agate back and forth with the tides, gradually grinding sharp angular rock fragments into smooth rounded pebbles.

Cornish Agate Jewellery

Having collected and sorted the agates, the first step in making the jewellery is to make a slice to check the pattern within. Ben [Church] uses a saw with a 25cm diameter diamond blade, which cuts about 10cm an hour. The blade is lubricated and cooled with honing oil that gives a smooth satin surface and is wonderfully tactile. It can take several hours to prepare and make the first cut through one of the larger pebbles.

We assess each slice individually, inspired by the unique pattern of each agate, to decide whether to trim and polish a slice as an irregular shape (freedom form), or draw around set templates to produce oval and teardrop shapes for example. We then sort the slices to choose which will be made into cabochons, with a rounded upper surface, and which will be worked as polished, flat slices.

Left: Cally collecting Cornish agates. Right: Cornish grey agate slice on chord.

Initially the flat slices were made into freedom forms with a drilled hole so that agate slice could be worn on a leather cord. A later development was a surf board design with further accentuated the Cornish essence of the agate, fitting with the Cornish beach and surfing lifestyle.

Adding a sterling silver pinch ball and chain was the next development phase. This jewellery has Made in Cornwall accreditation, as we collect the Cornish agates from the north coast of Cornwall, as well as cutting, slicing, polishing, drilling and packaging the jewellery all within about 10 miles of where they have been found. Pieces have been exhibited at Made in Cornwall events and displayed in the Lander Gallery in Truro, Cornwall.

This year we also had some of the agates mounted in sterling silver bezels and displayed on sterling silver necklaces to enhance the natural beauty of the agates, whilst placing the agate in the content of fine jewellery.

The Infinite Wave Jewellery Collection

The latest range of jewellery is our Infinite Wave Cornish Agate Collection. We have used the waves of the Cornish coastline as our inspiration to design unique luxury pieces.


Left: Cornish caramel and Cornish cream agate polished pebble
. Right: A model wears jewellery design featuring Cornish agate

Having worked with gemstones and with the jewellery industry for more than 30 years, it has been a wonderful challenge and an exciting experience to bring together my love of gemstones and jewellery to design something so uniquely Cornish.

My vision for jewellery, as a consultant in sustainable mining and ethically sourced gemstones, is to design a collection that, in collaboration with jewellers' worldwide, would be produced using only Fair-mined and Fairtrade gold and platinum, and ethically sourced silver.

Find out more at cornishagates.co.uk

This article originally appeared in the Winter 2017 (Vol. 26 No.4) issue of Gems&Jewellery magazine

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops. If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image: Cornish grey agate slice © Ben Church. All images © Ben Church.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


 

Additional Info

Read more...

Discover the Storytelling Powers of Master Gem Carvers

Deborah Mazza FGA explores how contemporary gem carvers are continuing an age-old artistic tradition of storytelling through gemstones.

Once upon a time, in a land far, far away, there was...How often have we all heard these words? This is the most common beginning to a story that fires the imagination, transporting one into a magical world full of marvels and wonders, starting in our childhood and possibly continuing into adulthood. But, what has this to do with gemmology and gemstones? Well, let me tell you my story starting in Idar-Oberstein, a little town in Germany, where gem carvers continue to tell stories through stones, carrying on an old tradition that started in ancient times. Any good story has interesting characters, here are mine...

Erwin Pauly

In his little workshop in Veitsrodt (Idar-Oberstein), surrounded by nature, Erwin Pauly creates objects of beauty and is in very high demand by VIP's worldwide. He learned the art of gemstones carving from masters of the time and has now become a master carver in his own right. Erwin Pauly is generous in giving his insight and helping aspiring artists who want to learn from him, he trained his three sons who have now acquired their own worldwide fame, one of them in Hand-Ulrich Pauly whose works can be admired in Tucson.


Example cameos preformed from gemstones. Far left is a citrine preform by Bernd Munsteiner, worked as a cameo by Erwin. Note the use of Munsteiner's lines and circles in Erwin's creation. He uses the line as a divider between face and hair, working it to then develop in a wheat sheaf. The circles are then part of the hairstyle. Image credits Erwin Pauly.

Mr Pauly started out with traditional agate carvings, consisting of an oval cameo on layered agate with classical motifs, or head portraits either shown in profile or front view. These portraits are also of living people, and can now be admired in his studio or in the museums of Idar-Oberstein.

Erwin Pauly thinks of himself as an artist who speaks through gems. He wanted to break away from the classical oval carvings to tell his own stories, so he started introducing other cameo shapes. In some of these carvings the face or the hair breaks out of the confinement of the frame bringing a new contemporary quality to the piece and adding another essential part to the story. He also started using other gemstones for his creations, opal, ametrine, citrine, beryl, rock crystal, and collaborates with Bernd Munsteiner for some of his pieces.

Munsteiner

Munsteiner has become a very well-known name in the trade. At shows everyone rushes to visit the Munsteiner booth and admire the latest creations this workshop produces. Munsteiner's introduced something new to the trade; inspired by nature, they challenged conformity and tradition, embracing the inherent inclusions and irregularities in gemstones, which unleashed a wave of creativity in many new artists. Their understanding and feeling for gemstones seems to continue exactly where nature left off. Munsteiner is made up of Bernd Munsteiner, his son Tom, and Tom's wife Jutta who is a very talented jeweller and channels the mood set by the lapidary artist into individual jewellery pieces. The final designs that emerge from Munsteiner's gemstone sculptures remind one a little of the Bauhaus movement and minimalism due to the simply, unfussy lines in pieces. But there is much more behind these pieces than what meets the eye.

'Magic Eye', Brooch with a 43.95 ct citrine, agate and diamond in 18 ct yellow gold. Image credit Munsteiner.

Munsteiner uses the optic laws of refraction and reflection to produce interesting three-dimensional effects in pieces; highlighting that the essence of a crystal can be sft and organic, not just angular and hard. Munsteiner believes that nothing is more powerful than an idea, and sometimes this idea has to wait until the right gemstone, with the right set of inclusion in the right arrangement, comes along. Only then will it be able to tell us a story.

Bernd, Jutta and Tom Munsteiner. Image credit Munsteiner.

Herbert Klein

Nothing really prepares you for the surprise you feel when presented with this company's miniature creations, including leaves, flowers, blossoms, fish and mammals all carved out of various gemstones. The attention to detail is stunning, the cuteness of some almost unbearable. All these little creations, some no larger than a one Euro coin, appear to have a life of their own and tell a story, all with a certain sense of humour.


Carved animal creations with a stunning amount of detail engraved. Image credit D.Mazza.

The current artist-carver at Herbert Klein is Stefan Klein, who started as an engraver in his father's company and developed his skills. Stefan's creative process is long, leading to a perfect creation; he carefully studies pictures and films of the nature he intends to represent in his pieces, he establishes a connection with the piece until he declares it finished and only then reveals its fairy tale.

The smallest tourmaline frog, placed on a one Euro coin for scale. Image credit D.Mazza.

None of his pieces are exactly the same. They all have small differences, whether that is the materials used, the inclusions within or the representation chosen. Each aspect contributes to telling a fantastic tale.

Stefan Klein in his workshop. Image credit D.Mazza.

Conclusion

There are many more stories and tales I can tell you about these artists and their creations: Patrick Dreher, for example, creates stunning gemstone animal sculptures that seem to come to life as they give the effect of muscles rippling beneath the skin. Michael Peuster creates stories out of different materials, gemstones and elements put together, while Manfred Wild sees a single, lonely stone in a gem parcel, picks it up and creates a story around what he sees.

But these are all stories for another day.

To find out more please visit: erwin-pauly.com, munsteiner-cut.de and herbert-klein.de.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image Erwin working in his workshop in Veitsrodt. Image courtesy of D. Mazza.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


Additional Info

Read more...

Challenging Perceptions: Meet the Gem Cutters Thriving in Newcastle

Sarah Steele FGA DGA, visits a growing community of gem cutters in Newcastle who are quietly, but effectively, pushing boundaries.

When we think about the great gem centres of the world, Newcastle in the North East of England wouldn't necessarily spring to mind. There is however a growing community of gem cutters who are challenging our perception of the faceting industry, entering and doing extremely well in international competitions, and quietly cutting world class gems for both pleasure and profit.

The NE1 Faceters (a play on words standing for 'Anyone Faceters') was established in 2012 by Steve Smith and Paul Sampson. As members of the UK Faceters Guild, both were keen to pass on their knowledge to a younger generation so Steve, along with Paul a master goldsmith and keen faceter himself, decided to form a group open to promote the art of faceting within the UK.


The pavilion girdles of Sarah's synthetic Verneuil ruby unfortunately showing a textbook example of chatter marks.

The group is run on a not-for-profit basis but has within its membership a number of professional cutters. The membership has an age range from 11 to 87 from diverse backgrounds, many of them scientists or engineers as well as archaeologists and artists within the ranks. The group meets monthly to broaden their knowledge of gemmology, but they also run annual summer schools where members and visitors spend a weekend cutting together under supervision of Paul and Steve. For the past four summers, I have packed up my faceting machine and joined them for the weekend. As a gemmologist I believe that the best way to truly understand a gem species is to cut it yourself.

In June, I visited the Saint Marie Aux Mines Mineral Show and had purchased a half boule of synthetic Verneuil corundum for a mere €20. I was keen to see if I could cut a large stone at this year's faceting school. I have pre-formed the ruby back in my workshop so it was ready to drop on arrival in Newcastle.

As I cut the girdle of my stone I'm feeling rather smug, the clarity is good and there is no obvious colour zoning. As I move on to the pavilion facets, however, I notice a distinct difference in the feel of the stone on the diamond lap in two cutting plains. The design is an antique cushion square and two sides of the pavilion are beginning to look a different texture to those on the opposing sides. I change to a finer grit lap to begin with pre-polishing but the problem seems to be getting worse. Rather than polishing the problematic facets, chatter marks are appearing in increasing quantity. Steve advises me to touch the stone on the lap in only three spots rather than the fluid arc movement we would normally use. This can often cure this problem as the diamond is now only cutting in three distinctive planes. In the case of this stone however, the problem persisted.

Steve then asked me how I'd aligned the rough on the dopstick. I had assumed that the C-axis on a Verneuil boule was parallel to the longest axis. Rather embarrassingly I was then informed that the C-axis in the Verneuil product always lies within the plane along which the boule is split, though not necessarily parallel to the boule's length, so I'm probably polishing along at least one cleavage direction.

The only hope for this stone is to realign the table at a slight angle, re-dop and recut the pavilion. I decide to leave this for a later date and cut an amethyst aligned at the correct angle previously prepared by Steve. Mine isn't the only setback over the weekend, we have chipped culets, stone knocked off the dop (everyone's worst nightmare), extra facets, missing facets, facets cut on the wrong cog, poor polish, no polish - the list is endless.


Simone Muehlbayer receiving expert tuition from Steve Smith.

Paul and Steve offer one-to-one tuition over the weekend. Simone Muehlbayer has been allocated to Steve and is an amateur jeweller keen to cut her first stone. By Saturday evening she was very proud of her polished pavilion and girdle. Conversation at Saturday evening's annual barbeque revolves around the problems associated with faceting from a British perspective. Surprisingly, the major problem lies in the acquisition of the faceting machines themselves.

There are over a dozen of us participating over the weekend and no two machines are identical. Five of the machines are the GemMaster11 fac-Ette, a machine considered by many to be the Rolls Royce of faceting rigs. However, this machine has not been in production for many years. I imported my second hand machine from California four years ago which including duty was in excess of £4,000. The rights to the GemMaster 11 machine were purchased by Wyatt Yeager, a diamond prospector and fan of the machine. I spoke to him regarding his plans for future production and he told me that the costs are so prohibitive that he intends to manufacture to order only. A new machine is likely to retail at $6,000 and that is working on a tiny profit margin.

Steve tells me that in his opinion, many of the cheaper faceting machines on the market are simply not good enough quality to cut a stone to the exacting requirements required for competition and high end clients. As a result, many members with engineering expertise heavily modify their own machines, some members choosing to build from scratch. Steve and Paul are seriously considering producing and retailing a British machine but it is difficult to find the precision engineering companies at a cost that would be feasible. In the meantime, Steve and Paul manufacture their own metallic resin and soft type-metal laps which are machined perfectly flat. They also mix their own custom recipe diamond compounds specific to the gem species they are polishing.


Simone Muehlbayer's brilliant cut citrine, featuring a feather in the girdle duplicated many times when viewed through the table.

By Sunday evening Simone has produced a fantastic brilliant-cut citrine that Steve confirms to be considerably better than a commercial cut stone. Unfortunately, a feather in the pavilion is giving an interesting fingerprint look when viewed through the table but she is rightly proud of her achievement. I don't leave with the 20 ct ruby I'd hoped for but I am happy with my modified emerald-cut amethyst and as usual have learnt a vast amount about cutting.

The NE1 Faceters can be contacted at nei1info@btinternet.com to discuss cutting projects and any unused faceting machines would be gratefully received.

All images courtesy of Sarah Steele.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image of Gemma McFarlane, Sarah Steele and Nigel Wilson cutting on their respective machines. Image: ©Sarah Steele


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


Additional Info

Read more...

Discover Two Bewitching Cameos at the Natural History Museum, London

First published in The Journal of Gemmology Vol.35/No.8, Robin Hansen FGA, gem curator at the Natural History Museum, London, takes us through the gemmological, mineralogical and historical background of two fascinating cameos from the late 1800s.

The collections of the Natural History Museum (NHM) in London include minerals, gemstones, worked objects and carvings. I recently had the pleasure to study two chalcedony/agate cameos that were fascinating for their gemmological, mineralogical and historical interest. What made both so delightful was that they had been carved onto the exterior of geodes. Both were purchased from gem carver Wilhelm Schmidt by the Geological Museum of the British Geological Survey in the late 1800s; the specimens then became part of the NHM collection in 1985.

Wilhelm Schmidt (1845-1938) was born in Idar (now part of Idar-Oberstein, Germany). At the age of 15 he was sent to Paris as an apprentice to learn the craft of gem engraving, under the masterful eye of cameo cutter Arsène. He was trained in the neo-classical style, but stone cameos were going out of fashion when he graduated in the 1860s.

Although Romanticism brought in new trends of Renaissance subjects for cameos, Schmidt's interest waned and he returned to Germany. Following the Franco-Prussia War in 1870 and subsequent events, Wilhelm moved to England with his brother Louis, where he changed his name to William.

The brothers set up a business in Hatton Garden that ran from 1872 to 1915 (Seidmann, 1988). During this time William regularly sold cameos, intaglios and carvings to the Geological Museum. His work was of interest because he utilised more unusual materials such as labradorite, moonstone and opal.


Figure 2. This cameo, also by Wilhelm Schmidt, depicts the head of Jupiter and is carved on the exterior of an agate geode. Specimen BM.1985,M16225; courtesy of NHM London © The Trustees of the Natural History Museum, London.

Of the two cameos documented here, the first specimen is BM.1985,MI5547, described in the museum's handwritten register as 'Cameo in Agate-Jasper on Amethyst' (see cover image). Depicting a Roman man with a wreath on his head, Schmidt carved the layer just beneath the amethyst druse, which consisted of pale orangey pink chalcedony containing fine crisscrossing dark veinlets and a few thin linear arrays of red iron-oxide spots. The layer of chalcedony continues into the background of the carving, giving a halo effect. The amethyst creates a simple dark backdrop, and it is a surprise to most viewers to find the centimetre-sized amethyst crystals on the back-side of the piece.

The terminations of many of the crystals have been ground away, presumably to give the cameo a more even surface. The object measures 78 x 66 x 38mm and was purchased from W. Schmidt on 23 December 1886 for £8. Although no location is given for the source of the raw material, it is likely to have been Rio Grande do Sul in Brazil, well known for its amethyst, agate and jasper, as well as its connections with Idar-Oberstein in the 1800s.

The second cameo, BM.1985,MI6225, is described in the museum's register as 'Head of Jupiter (after the antique) cut on the exterior of a hollow Agate from Oberstein' (Figures 2&3). It is carved as the head of the Roman god Jupiter, with long flowing hair and beard. The agate is very pale purple to light beige and locally contains small, dark, translucent, angular areas. It also has very fine red veinlets and tiny spots with an iron-oxide appearance.


Figure 3. The same cameo by Wilhelm Schmidt showing the rear interior lined by quartz crystals. The raw material originated from Idar-Oberstein, Germany. Image courtesy of NHM London, © The Trustees of the Natural History Museum, London.

On the rear, a fine layering of the agate can be seen around the edges of a hollow geode lined by a druse of sparkling quartz crystals up to 3mm in size that range from colourless to an ever-so-slight hint of pale amethyst. The carving measures 55 x 38 x 27mm and was purchased by the Geological Museum on 25 March 1891 for £10.

Roman figures were a common theme for Schmidt, and the NHM collection includes other cameos that he carved with the head of Mars, several of Minerva and Julius Caesar and a bust of Britannicus.

Reference: Seidmann G., 1988. Wilhelm Schmidt: The last neo-classical gem-engraver. Apollo, No. 317, 12-16.

To find out more about the collections visit nhm.ac.uk.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image and figure 1: In the late 1800s, Wilhelm Schmidt carved this cameo of a Roman figure into chalcedony adjacent to amethyst crystals that originally formed part of a geode. This composite image shows four sides of the object. Specimen BM.1985,M15547, courtesy of NHM London, © The Trustees of the National History Museum, London.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


Additional Info

Read more...

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Garnet is recognised for its rich history as a favourite gemstone of Victorian royalty, Ancient Egyptian pharaohs and the Roman elite. Its painter’s palette of shades, varieties and hues makes it a popular choice for jewellery creations.

Garnet Colours

Garnet is commonly seen in a striking spectrum of red, from orange rust and deep-violet to rich royal reds reminiscent of a pomegranate fruit.

The term 'garnet' comes from the name ‘gernet’, a 14th century Middle English word meaning dark red, further deriving from the Latin 'granatum' meaning 'pomegranate'. This connection was probably made due to the resemblance of garnet crystals to the seeds of a pomegranate.

.
Demantoid garnet with clear horsetail inclusions. Image by Pat Daly.

Today, garnet is the term for a group of minerals found in various colours from the red pyrope garnet to the zesty green tsavorite garnet.

Read more: 5 Things to Consider Before Starting the Gem-A Gemmology Foundation

The range of garnet colours comes from trace metals such as manganese, iron or chromium. Variations in chemical composition between different species of garnet result in a range of hardness on the Mohs scale from 6.5-7.5.

Garnet Varieties

There are five main species of garnet that have the same crystal structure but slight differences in their chemical composition.

• Almandine Garnet: purple to orangey reds
• Pyrope Garnet: purples to orangey reds
• Spessartine Garnet: oranges to yellows
• Andradite Garnet: yellows to yellowish greens
• Grossularite Garnet: colourless to yellow, to orangey red, to vibrant green (rare)

Polariscope garnet peridotite. Image by Pat Daly.

Where Do Garnets Come From?

Garnets are commonly found in many countries worldwide, including Australia, India, Czech Republic, Myanmar, Brazil and Sri Lanka to name a few.

In the 19th century, garnet adorned many decorative creations of the famous jeweller Peter Carl Fabergé and was a gem highly favoured by the Russian royal family. Bohemia and Russia were documented as primary locations to source garnet throughout the 19th century. Today, Tanzania and Namibia are prized for their abundance of garnets.

Left: Spessartine garnet with feather inclusions. Right: Hessonite garnet with crystal inclusions. Images by Pat Daly.

Garnet Folklore and History

Garnet has an extensive history and rich ancient folklore that spreads across many eras. Legend has it that garnet - known as the ‘Gem of faith’ - has powers of good health, prosperity and peace.

Read more: Gem-A Confirm Oldest Known Carved Tourmaline

The bright and striking nature of garnet is thought to be fitting to the vibrant personalities of those born in the month of January. It is thought that individuals who wear this stone can enter the New Year with a sense of renewed purpose, hope and lasting happiness.

Garnet Meaning

This gemstone was once used as a talisman of victory and protection by those going into battle. Many warriors would wear the stone to ward off disease and would place it on their battle wounds as a catalyst for healing.

Read more: Hidden Treasures of the Gem-A Gemstones & Mineral Collection

Historical reference to garnet date back even further to the time of the Ancient Egyptians, who utilised the stone as inlays in their jewellery and decorative carvings. Garnet was also a popular choice for signet rings worn by the Ancient Romans, especially when carved into intaglios to seal important documents. Hailed for its health benefits, garnet was a prized possession for clergymen and nobility across many centuries.

Famous Garnet Jewellery

Today, garnet is used in a wide range of jewellery collections and bespoke pieces such as rings, statement pendants as well as tiaras. Its array of colours and transparency make for spectacular pieces of considerable value.

Read more: The History of Garnet in Antique Jewellery

One of the most famous examples of garnet jewellery to date is a pyrope garnet hair comb from the Victorian era, housed at the Smithsonian National Museum of Natural History. The pyrope garnets that embellish the tiara-shaped comb originated from the Bohemian Mines (now part of the Czech Republic). Rose-cut garnets were often mounted in gold plate or yellow gold - a popular style during the Victorian era.

Whether you are looking for a talisman of prosperity for 2020 or a gift for someone born in January, the fire and sparkle of garnets are timelessly beautiful.

A Malayan garnet with rutile needle inclusions. Image by Pat Daly.

Receive copies of Gem-A’s publications, Gems&Jewellery and The Journal of Gemmology by becoming a Gem-A Member.

What is Associate Membership of Gem-A? Find out here.

Our Short Courses and Workshops at the perfect way to enhance your gemmology knowledge in a short space of time. Find out more here.

Cover image: Almandine garnet with crystal inclusions. Image by Pat Daly © Gem-A.

Additional Info

Read more...

Glass Simulants of Gems and Enhancement of Natural Gem Materials in the 16th Century

Guy Lalous ACAM EG, summarises the state of making glass simulants of gems in the 16th Century, as well as exploring the historical information we have available on the enhancement of natural gem materials.

What about gem treatments?

Many gemstones can be treated to alter their colour and clarity. Today, gemmologists are confronted to a broad spectrum of treatments ranging from the simple to the highly sophisticated as well as the easily detected to the highly elusive. Treatments include: bleaching, coating, dying, fracture filling, heating, impregnation, high pressure, high temperature, irradiation, laser drilling and lattice diffusion.

What about the origins of gem treatments?

Heated carnelian was found in Tutankhamun's tomb-dating to at least 1300 B.C.C. Plinius Secundus (First Century A.D) is the earliest written source on gem treatments. Pliny discusses many gemstone-enhancement techniques including foils, oiling and dying that are still in use today, almost 2,000 years later. The "Stockholm Papyrus" made about 400 A.D. in Greek-speaking Egypt contains 73 recipes which deal with the falsification of pearls and gemstones; representing the oldest extended recipe collection dealing with gems. In 1502 "The Mirror of Stones" was published, a fascinating book by Camillus Leonardus, a physician and astrologer of Pesaro, Italy. It discusses gem treatments and simulants and also how to identify those stones that are "not true" and the importance of experience and knowledge in this subject.

In the 17th Century, we have the Gemmarum et Lapidum Historia of 1609 by Boetius de Boot, a physician of Bruges. In the French translation of 1644, there is discussion in Chapters 20 to 22 of the decolourising by heat of sapphire, topaz, amethyst and the like, to produce diamond imitations; the dyeing of stones, mostly with metal compounds, an extended discussion of metal foils and an obscure description on how to harden gemstones. By 1820, agate dyeing in Idar-Oberstein had been perfected to the point that it was practiced on a large scale and the agate sold as treated stone. For the first time, a gemstone material was altered commercially and marketed as such and not as a natural material. By the middle of the 19th Century, gemmology had turned into a science (K. Nassau).

What about man-made glass?

Man-made glass dates back to approximately 5000-4000 BC, this took the form of glazes used for coating stone beads. It was not until 1500 BC that the first hollow glass container was made by covering a sand core with a layer of molten glass. Glass blowing became the most common way to make glass containers from the First Century BC. As from the First Century AD colourless glass was produced and coloured by the addition of colouring agents. Glass has been used as a substitute for emerald and other fine gemstones since at least the days of ancient Rome. Skills for glass making spread throughout Europe and the Middle East when the Roman Empire disintegrated. It was not until the full development of the Renaissance, in the mid-1500s, that a writer purposely gave the tedious details of the entire process of glass 'gem' making. This author was Giovan Battista Della Porta.


Figure 1: These 'emerald' and 'amethyst' glass eardrops in the Renaissance style were presumably assembled in the second half of the 16th century. The mounting is partially silvered copper. The green glass 'gems' are 6 mm in diameter. Courtesy of a private collection near Rome, Italy; photo by Carlotta Cardana.

Giovan Battista Della Porta was the first to publish in print recipes for making glass simulants of gems, in addition to information on the enhancement of natural gem materials. His Magiae Naturalis (1558), originally written in Latin, enjoyed vernacular translations in several European languages. The second, vastly improved edition (Della Porta, 1589), again in Latin, did not enjoy the same popularity - possibly because the first one has saturated the market or, alternatively, because the Catholic Church has enforced rules that made alchemy a forbidden practice and even the title Magiae became suspect. In spite of such restrictions, both editions contributed to making glass 'gems' popular decorative objects and to increasing their trade. During Baroque times, interest in glass 'gem' making reached an acme, and Della Porta's treatise was even translated into English in 1658.

Figure 2: This portrait of Giovan Battista Della Porta at the age of 50 is from the title plate of the 1589 edition of his Magiae Naturalis.

His modus operandi was well known. For every secret he learned, he first checked for other possible sources by reading books by old masters, after which he tested the results by performing experiments in his home laboratory. Glassmaking was one process that could be performed with a kiln, a rather simple apparatus. The preparation of certain special glasses (e.g. coloured ones suitable for simulating gems) involved knowledge that had been an artisan secret until it was released by Della Porta in his original 1558 edition of Magiae Naturalis.

In Book III of Magiae Naturalis, 1558, Della Porta wrote three chapters related to glass that followed the descriptions of other chemical operations, such as sublimation, distillation, purification and melting, plus miscellaneous recipes on how to repair broken corals, pearls and gemstones. He did not care to deal with how to make ordinary glass, but he proceeded directly to release the technicalities on how to prepare the special colourless glass that would be suitable for making coloured glass, so as to imitate gem materials. In chapter 16 he summarised the preliminaries, recommending the use of very finely ground silica mixed with fluxes.

In chapter 17 he made a digression aimed at explaining how natural gem materials acquire their colours and shifted to recipes on enhancing colour by using various natural pigments, by slowly diffusing them from the surface to the bulk of the gem under the slow action of fire. Then he returned to recipes intended to add weight to glass without modifying its hardness. In particular, he recommended adding lead to the already prepared colourless glass only while it melts, so as to increase its brilliance and weight. After another digression, he ended Chapter 18 with a series of explanations on how to obtain attractive 'gem' glass by carefully mixing colourless glass with pigments while it melts. The resulting gem simulants would resemble diamond, emerald, sapphire, pyrope, topaz, olivine, chalcedony, etc. The final recommendation was that the crucible containing the molten mix should be kept under close supervision, as excess heating would make the colour fade away.

In 1589, Della Porta, by now a mature scientist, reworked his Magiae Naturalis, expanding it from four books to 20. The in-folio sized text dealing with gems grew from five ordinary pages to a complete Book VI encompassing 10 dense pages and distributed over 13 chapters. Actually, only Chapters 1 to 5 concern glass gem simulants and Chapters 7 to 13 mostly concern the enhancement of gem materials. Everything is described in much greater detail than in the previous edition. After an introduction, Della Portas begins Chapter 1 with a careful description for the preparation of reagents for glass gem making, beginning with two fluxes. Chapter 2 recalls that silica is the main constituent of any glass gem. The raw silica can be either crystal or flint, or even round pebbles; the best of are said to be those gathered from the river Thames.

Chapter 3 describes in detail the furnace and the instruments to be used and Chapter 4 teaches how to prepare pigments. Chapter 5 is the core of the entire process. Indeed, it is titles "How gems are coloured". The pigments are blended with the previously prepared colourless glass while it is molten, so that they mix homogeneously. The recipe for glass used to simulate emerald is given last because the preparation requires a long exposure to fire. The following chapters describe various enhancements of natural gem materials and then move onto enamels, coloured metal sheets for reflection, etc. The author ends book VI, Chapter 13, with the short but factual statement: "This is all what we experimented on gems so far".


Figure 3: The title page of Magiae Naturalis Libri XX, 1589 edition, shows the titles of all 20 books composing this volume.

The second half of the 17th Century in England was characterised by an economic revival with increasing interest for science in general, including those books penned by 'writers of secrets'. The practice of publishing 'secrets', although unwelcome to many, contributed to the development of both science and the economy. In particular, it is significant that Della Porta's Magiae Naturalis, intended for completely different purposes and contributing only poorly to the 'scientific revolution' because of its still rather alchemical bent, eventually helped speed up the English industrial revolution.

This is a summary of an article that originally appeared in The Journal of Gemmology entitled 'Counterfeiting Gems in the 16th Century: Giovan Battista Della Porta on Glass 'Gem' Making'' by Annibale Mottana 2017/Volume 35/ No. 7 pp. 652-666

Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.

If you would like to subscribe to Gems&Jewellery and The Journal of Gemmology please visit Membership.

Cover image: Title page of the first english translation of Natural Magick in 1658, the title page of Magiae Naturalis Libri XX, 1589 edition and the frontispiece of the english translation of Natural Magick, 1658.


The Fascinating History of Antique Turquoise Jewellery

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Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

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Highlights of Gem-A Conference 2019

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Birthstone Guide: Amethyst for Those Born in February

Gem-A gemmology tutor Lily Faber FGA EG explores the history of amethyst and its significance as the February birthstone.

Amethyst is a well-known, purple variety of quartz that is February’s birthstone. Fashioned pieces can vary from a lighter lavender to a deep, saturated purple.

In ancient Greece, it was believed that if worn or used as a drinking vessel, the wearer would be protected from becoming drunk, hence, its name is derived from the Greek words meaning “not drunken”.

Read more: What is the Meaning of Amethyst? 

It is also believed by some that the stone will bring you luck, serve as an antidote to poison, increase your intelligence and protect you from magic spells.


Amethyst quartz with ribbon-like inclusions. Image by Pat Daly.

Various localities include India, the USA, Australia and Brazil, which is one of the most important sources today. Historically, amethyst was mined in Siberia and Saxony (Germany).

Amethysts in History 

In keeping with February’s holiday of St. Valentine’s Day, it is said that St. Valentine wore a signet ring set with an amethyst intaglio carved with an image of Cupid.

Amethyst was also worn in the finger rings of bishops, and can be found in the Crown Jewels fashioned as a faceted orb sitting atop the Star of Africa diamond in the sovereign's sceptre.

Read more: A Quick Guide to the Crown Jewels at the Tower of London


Amethyst quartz with tiger stripe inclusions. Image by Pat Daly.

Historically, aristocratic and royal families the world over have prized the gem in different eras. One such monarch was Queen Alexandra, wife of King Edward VII, who owned a gorgeous amethyst tiara containing several high quality large, oval-shaped stones from the mines of Siberia.

Find Out More! Get Started with the Gem-A Gemmology Foundation Course

She also commissioned a necklace that could also be converted into a tiara. These pieces are sadly no longer in the Royal Collection as they were sold at auction in the 1940s.


Amethyst quartz jewellery set. Image by Pat Daly.

Amethyst Crystals, Inclusions and Colours

If sold as a rough specimen, amethysts are often seen as individual crystals with one broken end where it was detached from the host rock. More often, they are sold in the form of a geode cluster.

Geodes are cavities or pockets that are lined with many crystals of various sizes. Often, the colour is concentrated in the tips of the crystals, thus leading to a great variety in saturation of colour from pale to deep purple.

Read more: Gem Quality Amethyst From Rwanda

An inclusion that is typical, if not diagnostic of amethyst, is the tiger stripe. It is a healed fracture that can occur when the stone twins. Amethysts are either one consistent colour or have angular colour banding with alternating light and dark colour zones.

Amethyst Care and Caution

Amethyst is a relatively hard stone at 7 on the Mohs’ Scale of Hardness, but only just! It is softer than other stones like sapphires, and as such, can be susceptible to chips and fracture.

The colour of some stones can fade when exposed to sunlight, so take care if displaying in a vitrine or shop window. When cleaning, do not use an ultrasonic cleaner in case there are any small inclusions or internal fractures that may expand during cleaning. Use warm soapy water and a very soft brush to clear away dirt.

Read more Gem-A Birthstone Guides here

Do you want to know more about gemstones and the study of gemmology? Discover the Gem-A Workshops or speak to our Education team

Cover image: Amethyst crystal quartz with detachment marks. Image by Pat Daly, Gem-A.


The Fascinating History of Antique Turquoise Jewellery

The Fascinating History of Antique Turquoise Jewellery

In his third Gemstone Conversations column for Gems&Jewellery, Jewellery Historian and Valuer John Benjamin FGA DGA FIRV explores the fascinating history of turquoise and its use in jewellery design from the Shahs of Persia to the Art Deco design movement.

Read more


Birthstone Guide: Garnet For Those Born In January

Birthstone Guide: Garnet For Those Born In January

If you're lucky enough to be born in January, vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is very often untreated, making it a rarity in the gem world. 

Read more


Getting Started with Quartz Inclusions

Getting Started with Quartz Inclusions

Do you know your calcite inclusions from your dumortierite, epidote, fluorite and rutile? Here, Charles Bexfield FGA DGA EG explores some incredible quartz inclusions and explains what to look for when shopping for quartz specimens.

Read more


Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Understanding Iridescence: Opals, Pearls, Moonstones and Fractured Stones

Iridescence has to be one of the most mesmerising and magical optical effects seen in gemstones. But have you ever wondered how it occurs? Gem-A's Collection Curator Barbara Kolator FGA DGA shines a light on this fascinating optical effect and tells us about the gems that are most likely to display it.

Read more


Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Hidden Treasures: Highlights of Gem-A's Gemstones and Minerals Collection

Gem-A Gemmology Tutor Pat Daly FGA DGA offers us a glimpse at some of the more unusual items in Gem-A's Gemstones and Minerals Collection.

Read more


Tanzanite: The Contemporary December Birthstone

Tanzanite: The Contemporary December Birthstone

Are you looking for the perfect festive gift for a December baby? Gem-A tutor Lily Faber FGA DGA EG considers tanzanite – one of three birthstones for December – and shares how this relatively new gemstone compares to its purple and blue-hued rivals.

Read more


Birthstone Guide: Turquoise For Those Born In December

Birthstone Guide: Turquoise For Those Born In December

Beautiful blue turquoise is one of three birthstones for the month of December (in addition to zircon and tanzanite). It is enriched with real cultural significance that can be traced back thousands of years. Here, we explore the blue shades of turquoise and explain what makes this gemstone so special...

Read more


Understanding the Cat's Eye Effect in Gemstones

Understanding the Cat's Eye Effect in Gemstones

Chatoyancy is the gemmological name given to the curious optical effect in which a band of light is reflected in cabochon-cut gemstones, creating an appearance similar to light bouncing off a cat's eye. Gem-A's Collection Curator, Barbara Kolator FGA DGA explains chatoyancy and highlights some of the many gems in which it can occur.

Read more


Jade and its Importance in China

Jade and its Importance in China

Jade has long been revered by gem lovers internationally, but nowhere more so than in China. But what is it that makes this gemstone so special? Gem-A's Assistant Gemmology Tutor Dr Juliette Hibou FGA gives us an overview of jade, how to identify it and its significance in Chinese culture.

Read more


Highlights of Gem-A Conference 2019

Highlights of Gem-A Conference 2019

The Gem-A Conference is always the highlight of our gemmological calendar! If you didn’t manage to make it, we’ve put together a few of the highlights from this year’s event to fill you in on what you missed, and whet your appetite for Gem-A Conference 2020!

Read more


Additional Info

Read more...
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