Nuummite – the Origin of Colour

This article by Guy Lalous ACAM EG summarises a technical article from The Journal of Gemmology discussing the origin of colour and conditions of formation in violet-to-blue Nuummite from Simiuttat, Greenland. 

Nuummite is an iridescent orthoamphbiole rock found in the Nuuk Distruct in south-west Greenland. It has only been known in the trade since 1983. However, the rock is believed to have been formed in the Late Archean period more than three billion years ago. 

A study published in The Journal investigates the mechanism for the violet-to-blue diffraction colouration of the Simiuttat Nuummite, providing a petrological description of the rock and highlighting the metamorphic pressure-temperature (PT) conditions of its formation. The study concludes that the colour of Nuummite is not due to grain chemical variation, but to the spacing of exsolution lamellae in orthoamphibole.

Some gemstones are formed by microscopic layers of material that are stacked upon one another. When light interacts with the different stacks within the gem material it causes flashes of colour. This is called iridescence, which refers to the scattering and diffraction of light, the iridescent effect is seen in a few gemstones including labradorite, moonstone and Nuummite.  

Checkerboard-cut Nuummite gemstone, 57.73 ct showing long, thin, violet-to-blue prisms. Image courtesy of Tay Thye Sun.
Checkerboard-cut Nuummite gemstone, 57.73 ct, showing long, thin, violet-to-blue prisms. Image courtesy of Tay Thye Sun.

What is the difference between iridescence and diffraction?

Iridescence happens when light passes through a thin, transparent film with a different refractive index from the surrounding material. Thin-film interference of visible light occurs when light interacts with a lamellar material consisting of fine layers that have different refractive indices (RIs). In diffraction, light waves pass through a grating. Diffraction is caused by the bending, spreading and subsequent overlapping of a wave-front when passing through a tiny opening or openings in an otherwise opaque obstacle. Iridescence is frequently used to describe any diffraction and/or thin-film interference-related colour phenomena, as interference and diffraction in minerals are closely related and often occur together.  

Read more: Reconstructed Amber Broken Down

The RIs measured on a polished slice of Nuummite were 1.650–1.660, with a second shadow edge at approximately 1.54. Hydrostatic specific gravity (SG) measurements were 3.09 ± 0.01. The presence of amphibole-, biotite- and cordierite-rich areas explains the different refractometer readings, with values of about 1.66 being typical for orthoamphibole while the additional shadow edge of 1.54 originated from cordierite.  

Observation of the polished slice with a digital microscope showed laths of orthoamphiboles criss-crossing one another. The crystals displayed blue-to-violet flashes, which were only visible on {210} cleavages. The colours vanished when the crystal was tilted to an angle of 5–15° depending on the tilting axis, indicating a strong geometric control on the colouring phenomenon. The surface topography of the {210} cleavages might act as a diffraction grating that could contribute to the iridescence.  

Keyence digital microscope photos of a polished slice of Nuummite show criss-crossing orthoamphibole prisms in a dark matrix of cordierite and biotite. Image courtesy of L. Franz.
Keyence digital microscope image: polished Nuummite showing criss-crossing orthoamphibole prisms in a dark matrix of cordierite and biotite. Image courtesy of L. Franz.

Polarised microscopy of the thin section revealed a close inter-growth of prismatic orthoamphibole, granular cordierite (with weak pinitisation) and brown, strongly pleochroic biotite flakes. All minerals displayed a random orientation, the correct petrographic name of the investigated Nuummite is biotite-cordierite-anthophyllite granofels.   

What is a granofels?

A granofels is a metamorphic rock with prevailing granular-textured minerals lacking any alignment. The anhydrous mineral assemblages found in granofels are produced at the base of the crust, where the conditions lead to their formation. 

Read more: Gem Central Exploring Ruby Treatments with Julia Griffith FGA DGA EG

Phase diagram calculations show the stability field for the mineral assemblage at temperatures of 505-660°C and pressures below 6.4 kbar. The electron microprobe analysis (EMPA) data of the orthoamphibole crystals from the Nuummite samples plot at 590–600°C (±25°C) in the T–AlIV solvus diagram of Spear, constraining the minimum metamorphic temperature experienced by the rock.   

What is electron microprobe analysis (EMPA)? 

Electron microprobe analysis is an analytical technique that is used to establish the composition of small areas of a specimen. The method is non-destructive and utilises X-rays excited by an electron beam, incident on a flat surface of the sample. 

What do we know about the solvus diagram of spear?

Solvus thermometry involves phases that form a solid solution at high-T but that 'unmix' into separate phases during cooling. The composition of coexisting minerals with a solvus relationship is an indicator of temperature. Data on mineral assemblages can be obtained through EMPA. The existence of a solvus in the orthoamphiboles between low-Al anthophyllite and high-Al gedrite has been noted by several scientists decades ago. Frank S. Spear (1980) conducted research on orthoamphiboles. His conclusion was that careful declination of the solvus T-X space enables to estimate temperatures in samples where two orthoamphiboles coexist.    

Read more: Zircon from Vietnam: Properties and Heat Treatments

EMPA and Raman spectroscopy classify the orthoamphibole as an Al-rich anthophyllite. Raman spectroscopy of the orthoamphibole showed great similarities to gedrite in the RRUFF database.  

TEM image. Image courtesy of R. Wirth.
L: TEM image of violet-to-blue orthoamphibole shows alternating lamellae of anthophyllite and gedrite
R: In the electron diffraction pattern from the orthoamphibole shown (L), each spot along the crystallographic b-direction is split (e.g. see arrows).  Images courtesy of R. Wirth.

Transmission electron microscopy (TEM) images showed a continuous succession of alternating exsolution lamellae of anthophyllite (wide, dark grey bands) and gedrite (narrow, light grey lamellae), which also were revealed by analytical electron microscopy (AEM) chemical analyses. The exsolution lamellae may have formed during cooling after peak metamorphism, during reheating processes in the course of the intrusion of a granite complex or during later metamorphic overprint.  

What is transmission electron microscopy (TEM)?

TEM operates on the same basic principles as a conventional microscope but uses electrons instead of light. What can be seen with a conventional microscope is limited by the wavelengths of light. The much lower wavelengths of the electrons allow a resolution that is thousand times better than with a light microscope.

What is analytical electron microscopy (AEM)?

AEM refers to the collection of spectroscopic data in TEM based on various signals generated following the inelastic interaction of the incident electron beam with the sample. These signals can be used to identify and quantify the concentration of the elements present in the analysed area, map their distribution in the sample with high spatial resolution (down to 1 nm or better), and even determine their chemical state.

Mineral composition thin section Nuummite. Image courtesy L. Franz
Mineral composition thin section Nuummite with L: parallel polarisers R: crossed polarisers. Revealing randomly orientated orthoamphibole (oam), cordierite (crd), biotite (bt) and accessory ilmenite (ilm). Image courtesy L. Franz.

Conclusion

The iridescence of Nuummite is due to the interference of light reflected from sub-microscopic, alternating gedrite and anthophyllite exsolution lamellae. Average spacing of 124-133 nm between the lamellae will generate violet-to-blue diffraction colouration, a previous study indicated an average spacing of 180 nm gives rise to yellow iridescence. 

Acknowledgments

We sincerely thank Rex Guo for donating material for this research. We owe great thanks to Dr Nynke Keulen, Karsten Secher and Peter Appel of the Geological Survey of Denmark and Greenland (Copenhagen, Denmark) for providing information on the occurrence of Nuummite in Greenland. Thanks also to Willi Tschudin (Universität Basel) for preparing the thin section and polishing the slice of Nuummite. Finally, thanks to Anja Schreiber (GFZ Potsdam) for the careful preparation of the TEM slices. The manuscript was considerably improved by the suggestions of three anonymous reviewers. ■ 

This is a summary of an article that originally appeared in The Journal of Gemmology titled ‘Violet-to-Blue ‘Nuummite’ from Simiuttat, Greenland: Origin of Colour Appearance and Conditions of Formation’ by Leander Franz, Tay Thye Sun, Richard Wirth, Christian de Capitani and Loke Hui Ying  2016/Volume 35/ No. 4 pp. 330-339 

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 Keyence digital microscope image of polished Nummite to show an orthoamphibole prism displaying violet-to-blue colouration. Image courtesy of L. Franz. 


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...

Gem Central Delving into Organics with Maggie Campbell Pedersen FGA ABIPP

Gem-A president and organics expert Maggie Campbell Pedersen presented the April Gem Central at Gem-A headquarters. Angharad Kolator Baldwin reports on this fascinating evening.

As the author of Gem and Ornamental Materials of Organic Origin and Ivory, Maggie was appointed Gem-A president last year. Her Gem Central evening was split into an informative talk on organics followed by the opportunity to get the loupe out and admire the array of samples that Maggie had brought and from the Gem-A organics collection.

Amber

The talk began with a discussion about copal - an immature resin, and amber - the more mature variety. Maggie then gave a quick rundown of the visual differences between amber found in a few different localities. 

Read more: Reconstructed Amber Broken Down

Baltic amber

Baltic amber dating from about 35 million years ago is opaque or transparent. The surface of the amber darkens with age. 

Dominican amber

Dominican amber is about 15 million years old. Some has good fluorescence and it often has a lot of inclusions including insects or debris from the forest floor. It is often darker than Baltic amber.

Mexican amber 

Mexican amber is around 20 million years old and has less insect inclusions than Dominican amber. It can be so clear that it has the appearance of plastic, so you need to know what it is to appreciate it. Some has a stripy appearance caused by debris sticking to it when it formed.

Sample of amber. Image courtesy of Gem-A.
Necklace. Image courtesy of Gem-A.

Burmite 

Amber from Myanmar, so-called Burmite is 100 million years old and is from the Cretaceous Period. Burmite is one of the very few ambers which can occur in a true red colour. The red variety is rare and therefore valuable. 

Australian amber

Australian amber is a fairly new find, discovered in Cape York, Queensland.  The precise locality is still a secret but is known to be crocodile infested. Believed to be about 12 million years old it has a lower melting point than the other varieties of amber, meaning it is less durable. The long-term effect of polishing Australian amber is unknown. 

Identifying Amber

It is important for dealers to know what they are selling and to be able to spot synthetics and heat treatments. Many Bakelite necklaces have been falsely sold as amber. Maggie let us in on a good tip - as far as she is aware opaque red amber doesn’t exist. So if it is sold as such, be suspicious! 

Clarified Baltic amber coated in red dye and sold as red amber
Clarified Baltic amber coated in red dye and sold as red amber. Image courtesy of Maggie Campbell Pedersen. 

But you can also whip out the specific gravity test, place the suspected amber in saturated salt water - if it floats it is likely to be amber. But don’t forget to properly wash the salt out after, Maggie warned the audience! Otherwise when the water evaporates you will be left with white powder residue. 

Maggie also discussed amber treatments and the mysteries surrounding green Ethiopian amber. Next she moved on to talk about horn. 

Horn

Horn and tortoiseshell are made of keratin. Rhino horn is solid while other types of horn grow as a horny sheath on a bony protuberance. 

Horn Beads
Horn bead necklace. Image courtesy of Maggie Campbell Pedersen.

Differentiating types of horn 

It is possible to differentiate between rhino and other horns through simple observation. Rhino horn is solid throughout, whereas other horns, for example buffalo, are hollow for most of their length. It can be difficult to distinguish the tip of a buffalo horn from rhino horn in a small carving. 

Tortoiseshell

Tortoiseshell is taken from marine turtles including the hawksbill turtle, loggerhead turtle and green sea turtle. All species are endangered and it is important for traders to remember that tortoiseshell can only be sold if it is pre-1947 and has not been altered since then. It is also salient to remember that carbon dating cannot be relied upon to date the item as it gives an indication only of when the turtle died, not when the tortoiseshell was worked.  

Tortoiseshell box. Image courtesy of Maggie Campbell Pedersen.
Tortoiseshell box. Image courtesy of Maggie Campbell Pedersen.

Ivory

"We should not rush to a solution purely on the basis of emotions as it may not truly benefit the animals” the title of the most recent column by Maggie in the Spring issue of Gems&Jewellery, providing an update on the UK laws regarding organic materials such as ivory. Worth a read if you have not already seen it. 

During the talk Maggie commented on the current muddle regarding ivory laws, and appealed to Gem Central attendees to remember that "burning ivory items won’t bring the elephants back, in fact who would know if I were to burn the beads I am wearing? The most important thing you can do is not buy new ivory".

Read more: Gem Central Exploring Ruby Treatments with Julia Griffith FGA DGA EG

It is incredibly important to be able to tell the difference between different types of ivory, for example walrus and elephant. And for the auctioneers selling the items to know what they are selling. 

Back of walrus ivory carving, showing clearly the secondary dentine
Back of walrus ivory carving, showing clearly the secondary dentine. Image courtesy of Maggie Campbell Pedersen.

Anomalies can occur as these are organic products. Maggie showed us an image of a tooth with bubble-like inclusions, an occurrence that happened in a whole pod of sperm whales. 

Interested in finding out more about this fascinating subject? Don’t miss out on the Summer issue of Gems&Jewellery where Maggie has kindly agreed to discuss terminology pertaining to organics. Discussing the problems faced with tortoiseshell, and amber she clears up some misconceptions for Gem-A readers. 

Hosted once a month at Gem-A headquarters at Ely Place London, Gem Central evenings are a unique opportunity to learn from experts and meet fellow gemmology enthusiasts. Free for Gem-A members and students, or just £10 for non-members. ■

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

Interested in attending a Gem Central event? For more information about our upcoming Gem Central events visit the Gem Central page or email events@gem-a.com.

Cover image assortment of organic samples. Image courtesy  of 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...

Beginner's Guide: What Can Emerald Inclusions Tell Us About Origin?

Emerald has long been one of the world’s most popular and valuable gemstones. Since the times of the Ancient Egyptians, emeralds have been viewed as tokens of good fortune and harbingers of new beginnings and rebirth.

While emeralds are fascinating from a historical and culture perspective, they are equally exciting for gemmologists, particularly when it comes to characteristic inclusions.

Birthstones Guide: Emerald for those Born in May 

A variety of green beryl, the name 'emerald' is derived from the Greek word smaragdus (meaning green). The green colour of emerald is caused by traces of chromium, but vanadium may also be present in some stones.

Today, emeralds can be found in Colombia, Brazil, India, Pakistan, Siberia, South Africa, Zambia and Zimbabwe.

Read more: The 'Emerald Desert' of Western Australia

The inclusions contained in almost all natural emeralds are very useful in distinguishing them from synthetic emeralds and other green stones. The types of inclusions in some emeralds can offer an indication as to their origin - although this is certainly not a foolproof method.

Typical Emerald Inclusions 

As you examine more emeralds, either during your studies or out in the field, consider the following localities and the typical inclusions and features that material from these regions can present.

LocalityTypical Inclusion and Features
Colombia Three-phase inclusions (liquid-filled cavity containing a crystal and a gas bubble)
India Two-phase inclusions (liquid-filled cavity containing a gas bubble)
Zimbabwe Tremolite (usually fibrous or neddle-like crystals)
Siberia Needle-like crystals of actinolite
Many Localities Mica flakes, pyrite and calcite, and also colour zoning

Examples of these inclusions can be found in the images below, taken by Gem-A tutor, Pat Daly. 

Three-phase inclusion. Image courtesy of Pat Daly.
Three-phase inclusion in emerald. Image courtesy of Pat Daly.

Two-phase inclusion. Image courtesy of Pat Daly.
Two-phase inclusion. Image courtesy of Pat Daly.

 Needle-like inclusion. Image courtesy of Pat Daly.
Needle-like inclusion. Image courtesy of Pat Daly. 

Pyrite inclusion. Image courtesy of Pat Daly.
Pyrite inclusion. Image courtesy of Pat Daly. 
Mica inclusion. Image courtesy of Pat Daly.
Mica inclusion. Image courtesy of Pat Daly. 
Crystal inclusion. Image courtesy of Pat Daly.
Crystal inclusion. Image courtesy of Pat Daly.

When combined with other assessments, such as the refractive index and specific gravity, these inclusions can give an indication as to the country of origin. ■

Interested in finding out more about gemmology? Discover our courses and workshops here

Cover image needle-like inclusions in emerald. Image courtesy of Pat Daly. 


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...

Gem Central Sri Lanka - A Gem of an Island

An extraordinary number of Gem-A and NAJ members came to this month's Gem Central to hear Colin and Hilary Winter share their love and passion for Sri Lanka. Barbara Kolator FGA DGA reports on the evening.

This October Colin and Hilary Winter will be hosting a joint Gem-A and NAJ trip to Sri Lanka and the Gem Central on the evening 8 May was a taste of things to come.

Read more: Delving into Organics with Maggie Campbell Pedersen FGA ABIPP

We started off with a virtual tour of the island: a spectacular view of the flight into Colombo airport, followed by the Mount Lavinia Hotel, where the tour will be based. On the itinerary are trips to Kandy, Ratnapura and Galle to see not only gem mining, treating and trading areas but also local animals, plants and historic World Heritage sites.

Colin and Hilary really know the island well and their knowledge and love of it and the people, came across extremely vividly. Their enthusiasm wore off on me too and Sri Lanka really seems like the most remarkable place, with an ideal climate (18-32°C), charming people, luxurious hotels, tasty food, deserted beaches and not forgetting many, many beautiful gemstones. In other words the ideal destination for a group of gemmologists!

Contents of a gem parcel from Sri Lanka. Image courtesy of Elaine Ruddie.
Contents of a gem parcel from Sri Lanka. Image courtesy of Elaine Ruddie.

Naturally we all wanted to know about the mines and the gems. It was interesting to hear that most of the mining is done in the gem gravels which can be 30-40 m deep, requiring the gravel to be pumped out. All the work is done by hand with only basic equipment. When the minerals are worked out, they are put back with the area reverting back to farmland.

Garnet, quartz and zircon can be bought easily and cheaply and set into jewellery, at a very reasonable price (with a bit of haggling) within 24 hours.


It was a fascinating evening with something for everyone, particularly for those interested in embarking upon an adventure.

Interested in attending this trip of a lifetime?

For anyone in the jewellery industry, nothing beats seeing and handling gems in their natural state, in their country of origin.

This is why Gem-A and the NAJ are offering members the chance of a lifetime to embark upon a trip to Sri Lanka.

A two week escorted tour, with fantastic opportunities to buy gems, visit mines and see gem cutters in action, including a 4x4 safari.

Date

Departure: 16 October 2017

Cost

£2,250 per person, based on two people sharing (single supplement £550). Deposits of £1,250 per person are currently being taken. This price is inclusive of economy class flights by Sri Lankan Airways from London Heathrow. Please note you will require money for meals and any gems you would like to purchase.

You will require your own travel insurance for the trip and visa for Sri Lanka, your passport must be valid until May 2018 (six months after you are due to return from the trip). Your insurance details will be required eight weeks prior to departure. 

Interested in registering for this incredible adventure? Contact the NAJ membership department 0121 237 1109.■

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

Interested in attending a Gem Central event? For more information about our upcoming Gem Central events visit the Gem Central page or email events@gem-a.com.

Cover image sunset in Sri Lanka


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...

What Makes the Alexandrite Colour-Change Effect so Special?

Sometimes known as ‘emerald by day, ruby by night,’ the gemstone alexandrite is a marvel of nature and the alternative birthstone for those born in June. Here, Julia Griffith FGA DGA EG explores the history, properties and colour change effect of this fascinating gem.

Alexandrite is an extraordinary gemstone that appears green or red dependent on the light it is observed under. This colour change effect is sometimes referred to as the ‘alexandrite effect’. The rarity of this material and its chameleon-like qualities make alexandrite one of the world’s most desirable gemstones.

What Makes Alexandrite Valuable?

Alexandrite was discovered in 1834 alongside beryls within the prestigious emerald mines of the Russian Ural Mountains. It is part of the chrysoberyl family, which is separate to beryls, being a beryllium aluminium oxide as opposed to a silicate. Chrysoberyls have good durability and a hardness of 8.5 on the Mohs scale, making them perfect for use in jewellery. This all depends, however, on whether you can find an alexandrite to begin with!

Alexandrite Gem A Conference Evan Caplan Photographed at the Gem A Conference 2017 Gem A BlogA large alexandrite specimen presented by Evan Caplan at the Gem-A Conference 2017. Photograph by S Dowthwaite FGA DGA on Instagram.

Alexandrite is so rare that it has never truly been the main aim of commercial mining. Instead, it is a happy ‘by-product’ as the likelihood of uncovering it in any significant quantity is very, very slim. In Russia, just one crystal of alexandrite was found for every hundred-or-so emeralds.

Read more: What Can Emerald Inclusions Tell Us About Origin?

Clarity is poor in the majority of alexandrites – they are commonly riddled with fractures and appear translucent to opaque. Such specimens have little value and are often unusable as gems in jewellery. Rough specimens over five carats in weight are also scarce and most alexandrites found on the market are under one carat. Prices for fine specimens above a single carat will rival or surpass fine quality rubies, emeralds and even diamonds, making them one of the most expensive and rare gemstones in the world.

The Alexandrite Colour Change Effect

The most important factor for alexandrite is the quality of its colour change. The most prized colour change is a strong raspberry red in incandescent light and a bright green in daylight - however an absolutely perfect specimen is not known to exist!

Alexandrite in daylight gamma rayAlexandrite photographed in daylight.

Alexandrite in tungsten alpha rayAlexandrite photographed under incandescent light.

The colours seen in alexandrite are caused by chromium – the same colouring element that causes the red of ruby and the green of emerald. The amount of colour change observed is often given as a percentage - with a 100% colour change from one hue to the other being the most valuable. The hues seen can also vary; if they stray too far from the expected colours of alexandrite or if the amount of colour change seen is minor, the value will be significantly affected and it is debatable as to whether it can be classified as an alexandrite at all.

Read more: What Makes a Gemstone Rare?

The colour change effect is due to alexandrite transmitting green and red light equally. Incandescent and daylight light sources are richer in different wavelengths (red or blue and green respectively) and this has a direct effect on what colour the gemstone appears to the human eye.

Alexandrite Pleochroism

Alexandrites are also noted for their strong pleochroism. This is an independent optical effect from colour change, in which the gem will appear different colours from different directions. In alexandrite the pleochroic colours are green, orange and purple-red.

Alexandrite Origin

The finest quality alexandrites are said to be from the original deposits in Russia, which were mined out in the 19th century. The name ‘Alexandrite’ was chosen to honour the Russian Tsar Alexander II. Legend states that this rare and beautiful stone was found on the day the heir became of age on his 16th birthday.
The vibrant red and green colours observed also mirror the colours of the national military of Imperial Russia. This led to alexandrite being named the official stone of the Tsardom of Russia.

Chrysoberyl AlexandriteAnother example of the colour change effect in alexandrite.

According to Russian legend, wearers of alexandrite reap many benefits including good luck, good fortune and love. A popular belief is that alexandrite helps the wearer strive towards excellence by bringing concentration, discipline and self-control.

Nowadays, alexandrites are mined from Brazil, Myanmar, Tanzania, India and Madagascar. Sri Lanka has also produced some fine specimens - the world’s largest faceted alexandrite hailed from this locality and is a whopping 65.7 carats. A further rarity is chatoyant or ‘cat’s-eye’ alexandrites, which are cut in cabochon to reveal this optical effect.

Alexandrite Synthetics

Alexandrite has such extreme rarity that those seen on the market might not be quite what they seem. Alexandrite has been successfully synthesised in laboratories since the 1960s and these synthetics have the same chemical, physical and optical properties of natural alexandrite and show a strong colour change.

The most common simulant is synthetic colour change sapphire, which shows a greyish blue to pink colour change. At just a dollar or two per carat - it is extremely common on the market. This material has been made since 1909, so is often found in antique pieces of jewellery.

Chrysoberyl Alexandrite Synthetic Flux GemA 0200An example of synthetic alexandrite.

A good colour change, good quality, transparent natural alexandrite could easily cost the consumer a five figure sum per carat and beyond. This, however, is a fine price to pay for such a spectacular and exceptional gem. ■

Do you want to find out more about gemstones and understand their physical and optical properties? Start your gemmology journey with the Gem-A Gemmology Foundation course.

Save the date! The Gem-A Conference takes place annually in November. Find out more about this year's Gem-A Conference, here.

Cover image: Gemmology in action at Gem-A. Image by Henry Mesa.

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Exploring Inclusions in a Twelve Point Black Star Sapphire

This article by Guy Lalous ACAM EG summarises a technical article from The Journal of Gemmology discussing a giant 12-rayed black star sapphire from Sri Lanka with asterism caused by ilmenite inclusions.

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. 

What is exsolution?

Exsolution in mineralogy is a process where an initially homogeneous solid solution separates into at least two different crystalline minerals without the addition or removal of any material. In most cases, it occurs upon cooling below the temperature of mutual solubility. 

Read more: Sri Lanka - A Gem of an Island

How does the exsolution process of rutile occur in star corundum?

At temperatures of 1200-1400°C, titanium moves through the resulting expanded crystal lattice and between the oxygen atoms, exsolving into rutile needles. Other frequently encountered oriented oxide inclusions are hematite (Fe2O3) and ilmenite (FeTiO3).

What is asterism?

Asterism is the star effect seen by reflection and scattering of light in cabochon-cut stones with suitably oriented rod-like inclusions or platelets. In corundum, due to the three-fold rotational symmetry of the basal pinacoid, networks of exsoluted syngenetic inclusions are oriented in three different crystallographic directions that intersect at 120°. The star image results from the incoherent superposition of reflected Frauhofer diffraction patterns, which arise when light is scattered around the network of inclusions. The cabochon in facts as a biconvex lens, which focuses the star image above the gem.  

What causes the asterism in 12-rayed black-star sapphires from Thailand?

Black star sapphires from Thailand contain inclusion networks of both the hematite-ilmenite series and rutile. The Fe-Ti epigenetic inclusions crystallise due to the presence of impurities of Fe and Ti in the host crystal as it cools after its formation, forming microscopic needles and platelets. The additional network of rutile needles parallel to the second hexagonal prism of the corundum host produces the second six-rayed star at 30° with respect to the first one. The observer will see a white six-rayed star perpendicularly superimposed over a yellow/golden six-rayed star.  

This study is about a large 112.64 ct ‘Ceylon Stars’ black sapphire of probable Sri Lankan origin that exhibits 12-rayed asterism. Raman spectroscopy combined with optical microscopy has been used to analyse both networks of needle inclusions in this sapphire as well as in smaller samples from the same source and in a black star sapphire from Thailand for comparison. 

Read more: Reconstructed Amber Broken Down

Raman spectroscopy surprisingly identified both networks of acicular inclusions in the giant 12-rayed black star sapphire as ilmenite. Typical Raman spectra for the ilmenite inclusions were characterized by a strong band at 678 cm−1. The other vibration modes for ilmenite were 162, 194, 221, 256, 291, 329, 374, 451 and 597 cm−1. The obtained spectra are in good agreement with natural ilmenite. The acicular inclusions parallel to the first-order hexagonal prism in each of the smaller 12-rayed star sapphires from Sri Lanka were identified as ilmenite by Raman spectroscopy. Ilmenite also constituted the second set except for one sample in which the second network consisted exclusively of rutile needles. Raman spectroscopy confirmed the presence of an Fe/Ti-rich oxide as well as rutile in the 12-rayed black star sapphire from Thailand.  

Raman spectra. Journal digest.
For the large sapphire, Raman spectra are shown for the host corundum (a) the inclusions responsible for the 12-rayed star, identified as ilmenite, present as narrow (b) and thick (c) needles and/or platelets; and for black inclusions of ilmenite that are not related to the asterism (d). The ilmenite spectra are distinct from those of Fe/Ti-rich oxide acicular inclusions in black star sapphires from Thailand (e). The vertical dashed lines indicate the Raman peaks of corundum superimposed on those of the analysed inclusions.

Optical microscopy of the 12-rayed black star sapphire at high magnification near the surface of the cabochon revealed some details about the microstructure of the growth bands. Networks of oriented needles and platelets - in three different orientations intersecting at 60°/120° were present within the basal plane. Compared to the growth bands, most of the acicular inclusions were oriented perpendicular and oblique at 30, or parallel and oblique at 60°. The density and the width of inclusions varied in different areas of the stone. Also, the average width of the inclusions oriented perpendicular to the growth bands of the host corundum was narrower than the inclusions oriented parallel to the growth bands. This explains the difference in sharpness between the two six-rayed stars. The needles responsible for the two stars were similar in colour, resulting into 12 brownish rays. Some larger plate-like shaped black inclusions reminiscent of magnetite with edges parallel or perpendicular to the acicular inclusions were observed. Strong transmitted illumination revealed a mainly dark blue body colour with some areas showing a more violet hue.    

Growth zoning. Journal Digest.
Two networks of needles constitute the growth zoning in the large 12-rayed sapphire, oriented perpendicular (a) and parallel (b) to the growth bands in the host corundum. The corundum growth bands are horizontal in both images. Photomicrographs by T. N. Bui in brightfield illumination; field of view
400 × 300 μm.

The presence of a single mineral - ilmenite - as the cause of 12-rayed asterism in sapphire was documented here for the first time in the largest such gem known to the authors, a 112.64 ct black star sapphire of probable Sri Lankan origin. The sharpness of the rays correlates to the width of the inclusions, regardless of the identity of the mineral that causes them. The fact that it contains only ilmenite inclusions is consistent with its Sri Lankan origin, which is distinctive from the inclusion assemblage found in Thai stones. ■ 

This is a summary of an article that originally appeared in The Journal of Gemmology titled 'Large 12-Rayed Black Star Sapphire from Sri Lanka with Asterism Caused by Ilmenite Inclusions’ by Thanh Nhan Bui, Pascal Entremont and Jean-Pierre Gauthier 2017/Volume 35/ No. 5 pp. 430-435 

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 112.64 ct 'Ceylon Stars' sapphire, from the collection of P. Entremont, displays 12-rayed asterism, as shown here with pinpoint illumination positioned (a) over its centre and (b) obliquely. Images courtesy of P. Entremont. 


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...

Can Gemstones Bring Prosperity to Malawi?

Deborah Craig FGA DGA, head of the Africa Team at International Women in Mining (IWIM) and board member within the organisation, reports on her recent trip to Malawi.

Peaceful, democratic Malawi remains one of Africa’s least-developed countries. Yet this small landlocked place, affectionately known as ‘The Warm Heart of Africa’, sits within the Mozambique Belt, surrounded by its famous gemstone-producing neighbours: Tanzania, Zambia and Mozambique. 

Read more: Ruby and Pink Sapphire from Aappaluttoq, Greenland

What is Malawi’s potential to join their ranks as a source of some of the world’s most beautiful coloured gemstones? Can Malawi’s nascent gemstone industry create prosperity for the country? In autumn 2016, Andrea Antonucci FGA and I travelled to Malawi to visit the Chimwadzulu Hill sapphire and ruby mine and meet with members of the local gemstone community. We began in Blantyre with John Chikokoto, the president of the Gemstone Association of Malawi (GAM). GAM was re-energised in 2015 with funding from the World Bank’s ‘Mining Governance and Growth Support Project’. 

Mr Chikokoto brought ruby and tourmaline crystals to show us. GAM members are mining sapphire, ruby, aquamarine, rhodolite, zircon and blue agate.

Ruby, from a new discovery at Makanjira, glow in the afternoon sunshine. Photo credit Deborah Craig.
Ruby, from a new discovery at Makanjira, glow in the afternoon sunshine. Photo credit Deborah Craig.

There is even a rumour that kimberlite has been discovered near the Mozambique border, but much of what we hear is merely speculation. The bulk of rough material is immediately exported out of Malawi, often illegally. Unlike Tanzania, Zambia and Mozambique, Malawi does not have a value-addition strategy, which would ensure more gemstones were processed in-country. He tells us if the gemstone industry is to grow, develop and provide long lasting economic benefits, his members need skills training at all stages of the value chain - mining, valuation, lapidary and marketing. 

These sentiments are echoed by Hellen Chasowa, regional chairperson south for Malawi’s Women in Mining Association (MAWIMA). GAM has around 2,000 members, of whom approximately 800 are women and also members of MAWIMA. Attracted to gemstone mining and dealing as an alternative to subsistence agriculture, which occupies most Malawians, MAWIMA’s members would also like to add value to the stones they are mining to increase their incomes and develop sustainable livelihoods. They are seeking project sponsorship for a tumbling machine and a drill, to make beads and create jewellery for Malawi’s burgeoning tourist trade. 

Read more: Discovering Unique Cameos of the Rainforest

Two companies, Nyala Mines Ltd and Columbia Gem House are working hand-in-hand to bring Malawi’s gemstones to the attention of the world market. Nyala Mines Ltd mines sapphire and ruby at Chimwadzulu Hill, and has created a fully-integrated, transparent supply chain extending from mine to retailer with its cutting, marketing and sales partner, Columbia Gem House. 

They would like the Nyala brand to equal quality, trust (disclosure of treatments) and social responsibility. The last is of critical importance when engaging with the economically disadvantaged communities close to the mine. Nyala works together with community leaders to understand how best to provide local support. To date, Nyala has built new school blocks, constructed boreholes for wells and upgraded the local health clinic. 

A warm welcome at the Kandoma school. Photo credit Andrea Antonucci.
A warm welcome at the Kandoma school. Photo credit Andrea Antonucci.

Chimwadzulu Hill is an eluvial corundum deposit discovered in 1958 about 145 miles south of Lilongwe, Malawi’s capital. The heavy minerals have been eroded by in-situ weathering and scattered down the sides of the hill, like sprinkles on top of an ice cream cone.

View from Chimwadzulu Hill. Photo credit Deborah Craig.
View from Chimwadzulu Hill. Photo credit Deborah Craig.

The presence of both chromium and iron mean that corundum is found here in a rainbow of colours: pale green, blue and yellow sapphires, but rubies and padparadscha sapphires are also found here. 

Over the years, the government, as well as various investors, have mined the deposit with varying degrees of success. In 2008, Nyala Mines Ltd acquired Chimwadzulu Hill, but the financial crisis, combined with rampant theft and high operating costs forced the mine to close. In 2013, Malawian national Abdul Mahomed acquired 80% of Nyala Mines Ltd bringing new life to the mine. Columbia Gem House, which had partnered with previous owners, reaffirmed their commitment to cut and market the stones. 

Chimwadzulu Hill is primarily a low-grade (in terms of carats per tonne) sapphire deposit; the rubies and padparadschas are a welcome bonus. The key to ensuring the mine’s profitability is to increase the volume of ore excavated and processed, thereby bringing down the mine’s operating cost per tonne. 

A beautiful 4.71 ct blue sapphire from the deposit, now in the Smithsonian Gem Gallery. Photo courtesy of Columbia Gem House.
A beautiful 4.71 ct blue sapphire from the deposit, now in the Smithsonian Gem Gallery. Photo courtesy of Columbia Gem House.

The current plant processes 30 tonnes of ore per day. Mr Mahomed would like to increase production significantly to 1,000 tonnes of ore per day. The new plant and equipment has been ordered and an environmental impact assessment has been filed, pending government approval. An increase in production will also hasten the removal of the overlying secondary deposits, hopefully exposing the primary source of corundum that Mr Mahomed believes lies below. 

Read more: Gem Central Exploring Ruby Treatments with Julia Griffith FGA DGA EG

It is time for Malawian gemstones to take their rightful place among the most beautiful gemstones in the world, while providing economic opportunity to Malawians. For this to happen, it is critical that the Malawian government implements value-addition strategies that ensure more rough material stays in-country to be cut and fashioned. There will be challenges, but small steps in skills training and market development can be taken at the local level, through associations such as GAM and MAWIMA, supported by Malawian and international partners. Nyala and Columbia Gem House have shown that operating in an ethical manner creates important benefits for local communities, as well as making good business sense. 

Deborah Craig would like to acknowledge the financial contribution of the Swedish Gemmological Society who helped make the trip possible. ■ 

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 L-R John Chikokoto, Deborah Craig, Hellen Chasowa, Andrea Antonucci. Photo credit 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...

Exploring a Spectrum of Diamonds with the Aurora Pyramid of Hope

Curator Alan Bronstein reveals how the world-renowned Aurora Pyramid of Hope evolved and shares the story behind his lifelong passion for coloured diamonds. 

Diamonds shown are between 0.5-1.5 ct. Copyright Aurora Gems Inc. Image courtesy of Robert Weldon.
Diamonds shown are between 0.5-1.5 ct. Copyright Aurora Gems Inc. Image courtesy of Robert Weldon.

It is difficult to trace all the challenges, twists and turns, triumphs and failures, which characterise the journey of a dream from fantasy to reality. For me, it all began with one experience, one stone, and one revelation. In 1977, as a college graduate who could not find a job, it was suggested by my mother Jeanette, the book-keeper at the New York Diamond Dealers Club, that I become a diamond broker. 

Such a job only required you try to sell loose colourless diamonds from one dealer to another. Such a job did not require any skills other than banging on doors (you could still do that in 1977) and getting offers on the diamonds you were soliciting. I found it to be one of the least fulfilling ways I could spend my time, as diamonds were already becoming commoditised by the price lists all diamond dealers carried. As a result, the illusion of what might be a visually beautiful stone disintegrated when it was deemed not to fit within the defined parameters of the emerging grading system, which qualified the stone on paper as a commodity. 

As fate often intervenes at the moment it is most necessary, just as I was about to make my break for the unknown, I saw something I had never seen in my years as a diamond broker; a yellow diamond that shined like the sun, hypnotising me and opening my mind to something new and exciting. Although it was part of the natural diamond world, it was a well-kept secret. Not because they had no beauty but because diamond dealers did not know how to make money with them, and thought they were the poor cousins to the 98% highly-promoted and coveted colourless diamonds. There were no discussions about them, they were never advertised and remained an underground trade that was only mentioned among the few aficionados in the diamond industry who collected them as curiosities, simply because they could not sell them. 

Into this small group of connoisseurs, I was embraced as a broker and as a peer because of my intuition for recognising the idiosyncrasies within the colours of the diamonds. This small group of mentors allowed me into their private world, and I learned what to keep my eyes open for from their experience and knowledge. This is the ultimate and true way to learn, from the wisdom of experts that have come before you. What a gift to be allowed to study among this exclusive club of dealmakers. 

Starting with Yellow Diamonds

The first thing I learned was not all yellow diamonds have the same colour characteristics. I saw all different colour reflections in almost every stone I looked at carefully. At this time, in 1980, the grading system so highly-regarded in colourless diamonds was generalised in coloured diamonds, to say the least. All yellowish diamonds were called yellow. All pinkish diamonds called pink. Yet when you had an opportunity to make comparisons, you could often see major differences in saturation and colour modifiers that were not identified by the labs. 

Instinctively, one could tell that the science of natural colour diamonds was in its infancy and that to determine a greater hierarchy of colours, perceived as more desirable, would be an advantage to finding, selecting, buying and selling the prettiest stones. It was the fork in the road I was travelling. 

The Aurora Pyramid of Hope collection - polished diamonds. Image courtesy of The Trustees of NHM, London.
The Aurora Pyramid of Hope collection - polished diamonds. Image courtesy of The Trustees of NHM, London.

I set out to find small sample stones that would be my standard for analysing differences that were hard to notice without comparison. These few small sample stones became the foundation for my business and for the concept that would become the Aurora Pyramid of Hope. 

Soon my interest and passion turned into an obsession. Every day I would enthusiastically go hunting for unusual diamonds as the colour matrix began to fill in. Often I would see something new, something different, quite often with dealers who did not know what to do with their curiosity. 

Soon I realised even though many stones had similar colour characteristics and intrinsic colours, when scrutinised subtle differences would become clearer leaning toward a spectral modifier. Even the shape and cut, angles and facet arrangements of the stone would change the appearance of the face up colour. 

Sourcing Coloured Diamonds 

This was a turning point, as I decided without the means to do so, that I would try to organise a collection with as many different colours as I could find, afford and obtain. The colour of the stones, many of which one would find extraordinary and many that were commonly seen, would be the primary driving force for gathering. Other factors like size, natural inclusions, and natural phenomena like fluorescence were secondary to trying to find stones that fit the universal matrix of colour in nature and specifically diamonds. 

For the last 37 years, beginning with the first sample stone to the present, I have collected 296 diamonds that now compose the Aurora Pyramid of Hope. The collection has gone through a metamorphosis in its composition and its meaning. It has served a great purpose for science, through studies of its colours at museums and laboratories around the world, and revealed many secrets that have advanced our understanding of these rare gemstones. 

Waterfall: Polished diamonds from the Aurora Pyramid of Hope collection. Copyright The Trustees of NHM, London. Image courtesy of Robert Weldon.
Waterfall: Polished diamonds from the Aurora Pyramid of Hope collection. Copyright The Trustees of NHM, London. Image courtesy of Robert Weldon.

As the colour matrix began to fill in, it took on a new meaning for me. At some moment my consciousness gave way to the concept that the pyramid was not just a science project but also a work of art in a new medium. A painting using only unmounted loose diamonds had never been seen before. 

Introducing the Aurora Pyramid of Hope 

I saw humanity in the collection as it grew. All the colours, shapes and inclusions were the perfect metaphor for all the races, colours, religions, faces of people and the infinite personalities that make us all individuals. I am also of the belief that we are related to diamonds, because we are made from the same essence created by the universe – carbon – the key element in all living things. Although natural diamonds seem inanimate, they reveal life through their brilliance. 

The pyramid shape itself has many spiritual and historical meanings that add to the symbolism I have tried to create. As does the name Aurora, the Roman goddess of the sunrise, and the colourful lights that appear at the northern and southern tips of the earth. 

When the collection was about to go on display at The American Museum of Natural History (AMNH) in New York, all the stones were in parcel paper and it was at this moment that I had to figure out how to present them. As I experimented with different forms, by laying out stones, it soon evolved naturally into the pyramid shape seen today. It unconsciously pulled me in that direction and I was pleased at its display and play of colours. 

I have many favourite stones in the collection; some for their stories and some for their extraordinary colours. One such amazing story is when a South American miner showed me a small rough diamond that was opaque and coated black. He had cut one flat surface into the stone so when you peered through this window it appeared green in colour. Many stones like this were colourless inside when you removed the skin coating the stone, which was caused by natural radiation in the ground. Other stones with this outer skin were often black or ground into diamond powder, because they were not considered gem material.

Green diamond: the original rough on the left and the finished stone emerald cut on the right. Copyright Aurora Gems Inc. Image courtesy of Robert Weldon.
Green diamond: the original rough on the left and the finished stone emerald cut on the right. Copyright Aurora Gems Inc. Image courtesy of Robert Weldon.

This particular stone was re-examined in the lab during the multiple phases of cutting over one year, to make sure it was the same specimen and that it had not been treated from the previous observation. At the end of the process, to my shock and that of the lab, it emerged as the most beautiful natural green diamond I have seen to this day.

The collection is, however, dynamic, and I have continued to collect and look for missing pieces to the puzzle. A further 36 stones were added in 2005 when the collection went on exhibit at the Natural History Museum (NHM) in London, joining the original 260 documented in 1998. I also replaced 20 stones that I felt would improve the variety and aesthetics of the original suite, thus the pyramid is greatly improved from its original museum exposure in 1989 at AMNH in New York where it spent 16 years. 

L-R Dr Jeffrey Post, Harry Rodman and Alan Bronstein in front of the Aurora Butterfly of Peace collection at the Smithsonian. Photo courtesy of Alan Bronstein.
L-R Dr Jeffrey Post, Harry Rodman and Alan Bronstein in front of the Aurora Butterfly of Peace collection at the Smithsonian. Photo courtesy of Alan Bronstein.

The Pyramid of Hope’s sister is the Aurora Butterfly of Peace; a collection evolved from the desire to make a pure artwork painting with natural colour diamonds. It was a 12 year process of building and arranging its mythic shape. Although the concept behind the pyramid began as science and became art, the butterfly began as an artwork and was also a bounty for science. It is proof that nature is science and art, and nature is the greatest artist of all. 

Along with its sister, the Aurora Pyramid of Hope is meant to be a universal non-secular artwork and symbol to point humanity to our common purpose for living; hope, peace and love. It serves as a legacy for all mankind. Alan Bronstein is the curator of the Aurora Pyramid of Hope with the financial assistance of his late step-father and business partner Harry Rodman. ■ 

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 From the Aurora Pyramid of Hope collection - rough and polished diamonds. Image courtesy of The Trustees of the NHM, London. 

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How to Assess the Value of an Opal: A Beginner's Guide to Pricing

Although once known as 'bad luck', opals are fast becoming one of the most sought after gemstones in jewellery collections. But what makes one opal worth thousands and others mere pounds and pence?

Here, Gem-A Instruments manager, Samatha Lloyd FGA EG, offers a quick but essential guide to opal value factors and what distinguishes a fantastic specimen from an average one. 

COLOURS IN OPAL

Opal is composed of uniform spheres of silica, which form a grid-like structure. The spaces between these spheres contain a silica solution. When light passes through the spheres and hits the silica solution, it is diffracted, producing differing rainbow hues.

Read more: The Different Types of Opal

Colour play depends on the size of the spheres, for example, smaller spheres result in blue colours, but orange and red will be present when they are larger. The more uniform the grid-like structure, the more intense the colours will appear.

Australian Opal. 

TYPES OF OPAL 

Customers may be most familiar with light opal, which makes up the majority of mined opal. It has base colours that range from white, to milky white and light grey, with varying degrees of colour play dancing on top.

If the body of the opal is transparent – also known as light crystal opal - the colour patches can be seen below the surface. It is these specimens that command exceptionally high prices. Your customers may also be familiar with black, or dark, opal, which has a dark body colour - sometimes enhancing the brilliance of the colours. This is the rarest and most valuable opal variety. 

OPAL VALUE FACTORS 

There are a number of factors that alter the value of opals. As mentioned, black opal can command higher price points than light opal (especially with an inky black body tone), although this is not to say that a fantastic light opal cannot be more expensive than a mediocre black opal. 

The brightness and brilliance of an opal is particularly important for its value, even if it is average in other areas. Therefore, lots of colours flashing on a dull stone may not command the same value as a gem with a higher degree of brilliance. 

Australian opal.
Australian opal.

We have already hinted at transparency, but this is also an important value factor. Light opal is much more desirable if it is transparent, with crystal opals with vibrant colours being particularly prized. 

A secondary and more complex layer of value arises when considering colours. The ‘dominant colour’ in an opal can affect its value, with red commanding the highest cost, followed by orange, yellow, green, blue, indigo and violet. However, do not forget, a blue-green brilliant stone will be more valuable than a dull red. 

OPAL PATTERNS 

In some rare cases, the diffraction of light within an opal can cause interesting patterns to arise. These patterns can increase the value of a stone. ‘Pinfire’ and small dot-like patterns are less desirable than bold ones, such as stripes, peacock feather shapes and broad brushstroke-like flashes of colour. 

Australian opal.
Australian opal.

 

ETHIOPIAN OPAL VS AUSTRALIAN OPAL

Customers may ask why one opal costs thousands of pounds, while another is mere hundreds or less. The answer could lie in its origin. Australia is a phenomenal source of opals and produces some of the world’s most incredible specimens.

Crucially, opals from this region have a lower water content, which means they are less susceptible to drying-out and less likely to exhibit ‘crazing’ - hairline fractures that impact the durability of the stone.

In contrast, Ethiopia is a newer source of opals, but some material has been found to have a much higher water content, making it unreliable and potentially unsuitable for jewellery. 

Ethiopian opal.
Ethiopian opal.

With thanks to Hatton Garden-based gemstone supplier, Marcus McCallum FGA, for taking these striking photos of Ethiopian and Australian opals.

Read more facts in The Opal Story by Andrew and Damien Cody, available in the Gem-A library. ■  

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 Short Courses or Workshops.

Cover image example of Australian opal. All images courtesy of Marcus McCallum. 

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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.

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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.

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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...

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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.

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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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Field Trip: The 'Emerald Desert' in Western Australia

Author, British jewellery designer and Gems&Jewellery contributor Joanna Angelett describes her recent gemmological trip to Western Australia.

We decided to take a trip to the 'Emerald Desert' in Western Australia, to look for emeralds. After arriving at Kalbarri National Park and spending a week, surrounded by its stunning pristine beauty, it was not a very short leap from there to our emerald destination - about 600 km – and setting off at 5am we reached Mount Magnet, renowned for iron and gold mining, before day-break.

Navigators on the way to the Emerald Desert.
Navigators on the way to the Emerald Desert.

To reach the Poona emerald mine we drove another 200 km from Mount Magnet to Yalgoo. Alluvial gold was discovered in Yalgoo in the early 1890s but then in the first part of the twentieth century, emeralds were discovered.

A variety of the mineral beryl (Be3Al2(SiO3)6)  - green in colour due to the traces of chromium or vanadium - were found in the Warda Warra in the Yalgoo Goldfields. But it is the Poona deposit, which has always been considered the most productive in the region. Several other, much less significant deposits like Noongal, Menzies and Warda Warra in the Yalgoo Goldfields (names from the Aboriginal language) discovered small unnamed occurrences of mostly milky-opaque emeralds, richly filled with cracks and inclusions and thus appeal mainly to mineral collectors, scattered across the Emerald Desert in a radius of more than 200 km around Poona.

The owners of our hotel told us they have relatives in almost every mining town of the Goldfields' surroundings, and locals filling the bar, mainly miners, gave us plenty of advice on how to reach the Poona emerald mine and how to prepare for this expedition. The owner gave us a present - a huge crowbar. "It will help," he said, and it really did!

Eugene Trimmer fossicking.
Eugene Trummer fossicking.

In the morning it seemed that the entire town knew "these people from London are going to dig for emeralds in the desert". They waved at us as we filled our 4x4 with endless bottles of mineral water, and even when we drove through the town.

Equipped with hand-drawn maps, it was just 150 km to Cue - a cosy town of 300 people - surrounded by golden mines, big and small, and then another 70 km on an uneven track to the mysteries of Poona's Aga Khan Emerald mine, named after a member of the Iranian royal family Sultan Aga Khan III. 

The gold mines with the highest productivity lie right on the doorstep of Cue and as soon as we passed this tiny, tidy town, we found ourselves in a land beautified with all shades of gold. It was impossible not to take photos of Cue's numerous gold mines from the distance and close up, especially after we were shown a huge gold nugget by a Cue resident, who had found it in the area several years ago and who ever since has worn a nugget around his neck as an amulet. 

Golden amulet belonging to a Cue resident.
Golden amulet belonging to a Cue resident.

We were told by locals that the best sign for those off fossicking, is to meet the potentate of the desert and master of all its treasures - the Golden Coins King - the beautiful and rare lizard 'dragon' of the Emerald Desert, who it is said leads to great fortune.

Golden Coins King of the Emerald Desert. Image courtesy of Eugene Trimmer.
Golden Coins King of the Emerald Desert. 

Certainly we had been waiting all the way for such a sign and when, we saw the Golden Coin King at first we did not believe our own eyes, but it was real. Even getting the opportunity to take a picture of the Golden Coin King was magical.

After a couple of miles along a narrow bumpy path, we finally discovered an abandoned runway and a bit further on, a now irrelevant warning: 'Danger Active Mining Area Keep Out'. One more mile and we were honoured by the chance to see and enjoy Pegmatite's field.

In Poona emeralds occur in both mica schist and quartz pegmatite matrix. The best emeralds were found here during the active mining period of 1960 to late 70s, in a mica schist adjacent to the quartzose beryl-bearing pegmatite, where some crystals were gem quality, and huge boulders of perfect quality snow-white quartz were found scattered across the area. 

Our mineral collectors' enthusiasm gradually shrunk as the day wore on and the hope of finding a huge sparkling transparent emerald of a saturated green began to shrink.

But sometimes a small surprise find can bring greater gratification than an expected large one, and it happened this time; we found a milky-green crystal, almost invisible amongst the mass of brightly coloured rocks sparking in the sun, but in our eyes it was invaluable.

Milky green emerald find.
Milky green crystal of emerald.

Sunny and golden Western Australia slowly abated into the bustling heart of London, where our designer studio is based in Hatton Garden and the arrival of the Poona emerald was eagerly awaited.

From the very beginning there was no doubt what kind of design this opaque emerald demanded, but primarily it was necessary to release it from the matrix. When dealing with one of the most fragile gems, this it is not an easy task.

Although some of Poona's crystals are gem quality, they are still quite undistinguished in size, with only one exception in 1971: an 138 carat transparent emerald was found and widely published in the WA press. Gemmologists Perry and Levinson were engaged to separate the emerald from the biotite matrix.

Despite their best efforts the stone cracked and split into two unequal parts of 118 and 20 carats. This type of matrix makes the extraction of emeralds very difficult, which made mining in Poona an unattractive commercial quality.

Gems Merchant with emerald rough ring from the collection 'The Characters' by Joanna Angelett. Image courtesy of Eugene Trimmer.
Gems Merchant with emerald rough ring from the collection 'The Characters' by Joanna Angelett. 

We remembered this story, when our emerald broke in two parts during our attempt to release the green jewel from the tenacious rock, but in this case it did not spoil our plan. The ‘Gems Merchant Captain’ ring shoulders half of the emerald and represents Poona’s rough supplied to Sultan Aga Khan III, telling the story of the wondrous emerald desert of Australia. ■ 

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 broken emerald. All images copyright of Joanna Angelett.


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...

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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.

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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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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.

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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: Peridot for Those Born in August

Those born in August have vibrant green peridot as their birthstone. Lily Faber FGA DGA EG delves into this zesty gemstone to find out more about its physical properties and fascinating history.

Peridot is the birthstone for August and is known for its rich green colour. It is one of the few gemstones that come in only one colour (green), and its name is thought to derive from the Arabic word ‘faridot’, which translates to ‘gem’. 

Rough Peridot Crystals GemARough peridot crystals. Image by Gem-A.

Peridot is a transparent gem variety of olivine. Coloured by iron, it comes in a range of greens from yellowy-green to brownish-green. It also has a slightly oily or greasy lustre, but don’t let that description put you off!

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

Its distinct olive-green hue is a lovely reminder of long summer days. In fact, some believe that peridot can bring happiness, luck and prosperity while calming anger, conquering fear and protecting one from evil spirits.

Peridot is formed in the Earth’s mantle and makes its way to the surface via volcanic eruptions. It is typically found in ancient lava beds. Occasionally, it can also come from outer space!

Mining for Peridot Gem A Blog August BirthstoneMining for peridot. Image by Gem-A.

A special type of meteorite called a pallasite meteorite sometimes contains peridot within its iron-nickel matrix. If you slice the meteorite open, it will reveal a smattering of transparent to translucent gems.

The History of Peridot

Zabargad Island (St. John’s Island), in the Red Sea off the coast of Egypt, is believed to be the earliest known source for peridot. Centuries ago, the Greeks called this island Topazios, which was also their name for peridot. Later, this island was mined for peridot to fill the coffers of Egyptian kings and anyone who tried to set foot on the island at that time was threatened with death.

It has been said that many of Cleopatra’s emeralds, her favourite gemstone, were actually peridot. Strangely, the ancient Romans called peridot the ‘Evening Emerald’ because they believed that its bright green colour could only be seen at night, which is clearly not the case!

Read more: What is the Link Between an Emerald and the Emerald Cut?

Other localities where peridot is found are Myanmar, Pakistan and the Peridot Mesa in the San Carlos Apache Native American Reservation in Arizona, USA.


Lilypad inclusions. Image by Pat Daly FGA, Gem-A.

The Physical Properties of Peridot

This is a brittle stone with a hardness of 6½, which leaves it vulnerable to chips and scratches. Care should be taken when set in jewellery, especially rings. Perfumes, hairspray and make-up can also damage the stone, so spritz your perfume prior to draping yourself in peridots.

Read more: Questions to Ask When Buying a Piece of Gemstone Jewellery

A characteristic feature that can help differentiate peridot from emeralds is its high birefringence of 0.036, within an RI range of 1.65 to 1.69. As a result, the internal inclusions and facet edges within the stone may appear ‘doubled’ – almost like you are looking at the gemstone with double vision. You can often see this doubling with a loupe or even with the unaided eye if the stone is big enough.

The most prized peridots are those of larger size, with a rich ‘oily’ green colour and few inclusions.


Mica inclusions. Image by Pat Daly FGA, Gem-A.

Peridot Inclusions

Common inclusions are lily pads, which consist of crystals, typically chromite, and are surrounded by curved stress cracks. Mica flakes can sometimes give a brownish tinge to the gem. Needle-like ludwigite inclusions are also seen.


Ludwigite and vonsenite inclusions. Image by Pat Daly FGA, Gem-A.

While this stone has gone in and out of fashion over the years, I encourage you to think of peridot for your next piece of jewellery not only for its gorgeous colour, but also for its interesting and varied history.

Read more: How to Identify Antique Edwardian Jewellery 

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

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

Cover Image: Peridot © GemA.

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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...

Fossicking in the Outback

Carmen Garcia-Carballido FGA DGA L.Geology MSc. EurGeol travelled to the southern hemisphere to find out more about the opals and sapphires of eastern Australia.

To test the skills acquired in two years training as a gemmologist with Gem-A, my husband planned a three week field trip to the sapphire and opal fields of eastern Australia.

We flew from Aberdeen to Sydney, hired a motorhome and headed into the outback of New South Wales (NSW) and Queensland. However, cyclone Debbie making landfall on the coast put paid to our plan to visit a gem dealer in Yepoon and check out the Marlborough Chrysoprase. To keep safe we stayed inland, driving 4,500 km in 13 days and camping at a different site every night.

Map of Australia showing key sapphire and opal locations and the field trip itinery. Image by Peter Scott-Wilson.

Two days from Sydney, our first gem field was Glenn Innes where we tried fossicking for the first time. A petrol station sold us a ‘bucket of dirt’ and rented sieves for AUS $20. Washing the dirt off, we found our first sapphires and zircons. We admired Robert Cook's collection of locally mined parti-colour sapphires that he cuts in his shop at the Visitor Information Centre. After some purchases, my husband had to drag me out of Robert’s shop.

60 km west at Inverell, we met Jack Wilson, who owns a longstanding sapphire mine and his wife Dallas, who designs lovely jewellery with blue sapphires from his mine. I bought some untreated rough blue sapphires with the idea of learning to cut them myself. Jack explained the host rock (i.e. the primary deposit where the sapphires formed) has not been identified. These sapphires are found in secondary, alluvial deposits.


Rough untreated sapphires from Jack Wilson's mine. L-R 10.21 ct and 6.54 ct.

After a long drive west, roads littered with dead kangaroos took us to Lightening Ridge, famous for its black opals. The town in the desert appeared empty. Tourists do not arrive until Easter. Only emus stay all year round. We camped in a site by the artesian baths, a wonderful way to relax and learn about the immense subterranean artesian system that probably played a role in the development of the opal fields. We visited an underground opal mine and were allowed to fossick for opals on the ‘mullock heaps’ of old spoil outside the mine. My husband found a small sample but I was not so lucky.

Next day we headed northwards. I was disappointed I could not buy any black opals in Lightning Ridge because the shops were shut, but a few kilometres before crossing into Queensland, a roadside sign led to the house, shop and workshop of Greg Armstrong. An opal miner, cutter and stone setter. Greg laid out his collection of white and black opal (3) and when we mentioned we were learning lapidary, he gave us a bag of ‘potch’ opal to practice cutting at home.

Boulder opals from Quilpie, mined and cut by Eddie Lunney.

Over the state boundary, we headed north for St. George, Roma, where the oil and gas industry’s mega coal bed methane (CBM) project produces gas from extensive Permian and Jurassic coal deposits to supply the energy needs of c. 90% of the homes in Queensland, and the location of the famous Carnarvon Gorge.

We drove inland to central Queensland to The Gemfields area, which includes the localities of Anakie, Rubyvale, Sapphire and Emerald, where green gemstones initially taken for emeralds were found in about 1880, when drilling for water, ahead of railway construction. Green and yellow sapphires and zircons have been mined in this area since the 1880s.

Read more: Field Trip: The 'Emerald Desert' in Western Australia

At the Sapphire Caravan Park we watched wallabies and lorikeets being fed. Taking Jack Wilson’s advice, we looked for Peter and Eileen Brown at the Rubyvale Gem Gallery, but as they were on holiday, the shop manager showed us Peter’s amazing fancy cuts on parti-colour sapphires. The shop is a gemmologist's paradise. Alicia Pray was cutting beautiful black star sapphire cabochons from the Desperado mine, and we bought a bag of ‘wash’ from the mine to fossick back home in Scotland.


Coloured sapphires collected over a period of 40 years in The Gemfields of Queensland by Peter Brown of the Rubyvale Gem Gallery.

Alan, a lively Stranraer émigré, took us round an underground sapphire mine in Rubyvale. Prospectors first dug one metre diameter vertical shafts through ‘shin cracker’ overburden (sandy gravels). The bottom layer of wash sits uncomfortably over eroded granite. When miners hit the granite at a depth of 15 m or so, they dug horizontal tunnels to follow the alluvial pay zone where sapphires, zircons, garnets and occasionally diamonds concentrate. Miners knew if they found a block of quartz in the wash, and sapphires were present, they were likely to aggregate upstream of such ‘Billy boulders’. This helped them to orientate their tunnels.

Geological section c.15m below the surface inside the Walk-in Miners Heritage Sapphire Mine at Rubyvale. The alluvial sapphires concentrate within narrow 'wash zones' (average 15-20 cm as marked by dotted lines) above the 'granite floor' and below several metres of sandy alluvial gravels. Elongated features are pickaxe marks.

From The Gemfields in Queensland, we drove westwards to Barcaldine ahead of cyclone Debbie's rainclouds. Here we decided to head south towards the Quilpie opal fields. As the land became more arid, the soil turned red, the gum trees thinned out and the grass grew sparse. Intrepid wildlife competed with massive ‘road trains’ for the driver’s attention on the empty roads between the gem locations. We passed trucks hauling three trailers, sometimes four.

Arriving in Quilpie, everywhere we went we were presented with useful information, friendly advice and ideas for things to see, and a chance to cool down from the 35 °C heat of early autumn in the outback. In Quilpie, they told us St. Finbarr’s Catholic Church was worth a look. Its altar, font and lectern have impressive panels of boulder opal donated in 1976 by local miner Des Burton, the father of the boulder opal industry. I was quite literally on my knees in adoration.

The only shop open in Quilpie sells everything. There I found the last copy of Greg Pardey’s Black Opal: A Comprehensive Guide to Cutting on its shelves and read it cover to cover before we got back to the UK. Walking back to the motorhome on our way out of town, we noticed that the Opal Hunter shop had opened too. Asking if I could buy some rough opal to cut back home, shop owner Eddy Lunney told me he would need to get to know me before knowing what he wanted to sell me. Induction into opal heaven started with a tour of the shop, the lapidary workshop and the yard with part of his huge stock of boulders from his opal mine. By teatime he had given me a masterclass in boulder opal cutting and polishing. I absolutely loved it! The dark blue and purple colours he brings out of the transparent opal (known as crystal) are gorgeous. It was really hard to leave Quilpie the next morning.

We noticed a change in the weather. The temperature had dropped to 20 °C as we drove to Yowah. In this famous opal location, we found Scott Shorten, shopkeeper, opal mine tour guide and librarian. After lunch, with his shopkeeper hat on, he showed us round the Yowah Opal Centre. Yowah opal is found inside nodules. Nine out of ten nodules are empty, so it is always exciting to crack open one, using a hammer or even better sawing through it, to see whether there is any opal inside. Scott sold us some good samples.

Before flying home, Matthew Morin FGA FCGmA senior sales consultant at Altmann + Cherny, a jewellers on Sydney’s Pitt Street, showed me how beautiful opals are used in modern jewellery (6). The shop also hosts The Olympic Australis, the largest and most valuable piece of opal ever found. It is a white opal from Coober Pedy, which weighs 17,000 ct, measuring 28 cm long by 11.5 cm high. For more information visit altmanncherny.com.au/famous

ACKNOWLEDGMENTS Carmen Garcia-Carballido would like to thank her husband, Peter Scott-Wilson, for organising the wonderful tour. Eddy and Lynda Lunney for their hospitality at Quilpie. Jack and Dallas Wilson, Robert Cook, Greg Armstrong, Scott Shorten, the staff at Rubyvale Gem Gallery and Matthew Morin for generously giving their time to discuss Australian gemstones.

Carmen meeting Matthew Morin at Sydney jewellers Altman + Cherny. Matthew is also the president of, and a gemmology tutor at the NSW division of the GAA (The Gemmological Association of Australia). Carmen is modelling a Koroit boulder opal pendant on white gold from the shop. Image by Peter Scott-Wilson.


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 Yowah boulder opals cut by Scott Shorten. Image by Carmen Garcia-Carballido.


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.

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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. 

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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.

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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.

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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.

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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...

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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.

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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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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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Birthstone Guide: Sapphire for Those Born in September

Legend describes sapphire as a stone of purity, honesty, trust and prosperity, bringing inner peace and protection to its wearer. From a gemmologist’s perspective, sapphire is an important variety of the mineral corundum and an integral part of the global trade in coloured gemstones. Here, we consider the many facets of sapphire, from inclusions and treatments to synthetics, engagement rings and royal connections.

Sapphire: The September Birthstone

Those born in September are lucky enough to count sapphire as their birthstone. This ‘royal’ gem is often described as one of the ‘big three’ – sapphire, ruby and emerald – or perhaps ‘big four’ – sapphire, ruby, emerald and tanzanite’ – in the world of coloured gemstones.

Sapphires have always been prized for their colour and are believed by some to bring their wearer wisdom and truth. Historically they were thought to attract divine favour, prevent the wearer from suffering envy, promote serenity and give one peace of mind. Often used in engagement rings, sapphires are an ancient symbol of fidelity.


Natural sapphire with crystals and feather inclusions.
Image: Pat Daly, © Gem-A.

The word sapphire originates from the Greek word sappheiros, meaning ‘blue stone’. Sapphires are traditionally associated with the colour blue but they can come in any colour aside from red, which would be a ruby. One of the most valuable colours of sapphire is a natural, untreated padparadscha (orangey pink), which means ‘lotus flower’ in Sinhalese.

Sapphire Origins

Sapphires are a variety of the mineral corundum – an aluminium oxide in the trigonal crystal system. These stones are most commonly sourced in Australia, Cambodia, Myanmar (Burma), Sri Lanka, Thailand and in some parts of Africa.

When mined in their natural rough form, sapphires can appear dark and dull until their true colour shines through once polished, cut or treated. The origins of sapphires can directly affect the clarity, carat, cut and colour of the stones and therefore determines their value and popularity to the trade.

Sapphires that are mined within Sri Lanka or Thailand have been considered by many to be the most valuable due to their clarity and brilliance of colour. Like many natural stones, it is the presence of visible inclusions within the crystal structure that can sometimes - but not always - indicate where in the world the sapphire has been mined.


A rough yellow sapphire crystal in bipyramid form.
Image: Pat Daly, ©Gem-A .

Sapphire Resilience

Measuring at nine on the Mohs scale of hardness, sapphire is well known for its good durability and refractive index of 1.76 to 1.78. The resilience of these stones makes them highly desirable not only for the fine jewellery market but also to industry for electronics and scientific instruments.

Due to its high ability to withstand scratching, sapphire is one of the most popular choices for engagement rings and other jewellery pieces for everyday wear.

Sapphire Engagement Rings

Today, sapphire has become the second most popular choice of gemstone after diamond for bridal jewellery and fine jewellery, collections. One of the world’s most famous sapphire jewellery pieces is the blue sapphire and diamond engagement ring given to Lady Diana by Prince Charles in 1981. Prince William proposed with this 18ct oval sapphire ring to his now wife, Kate Middleton, in 2010.

Colour Spectrum of Sapphire

Traditionally, sapphires are thought of as only appearing in naturally vivid blue. In fact, this gemstone can occur in a wide rainbow spectrum of colours; from canary yellow and tropical orange to fuchsia pink. The red variety of corundum is otherwise known as ruby.

Sapphires get their colour from different trace elements. The presence of iron and titanium are responsible for the blue tones, while traces of chromium cause pink tones. Ruby red is a result of more chromium present in a stone’s chemical structure.

Sapphire Clarity and Inclusions

Sapphires can be found as either well-defined crystals or water-worn pebbles, depending on the type of gem deposit. If well-formed, they will take the shape of a hexagonal bipyramid or hexagonal barrel-shape with striations running horizontally across the crystal faces. They are often colour-zoned across the crystal or with hexagonal zoning in their cores.


Sapphire with rutile inclusions that appear as silk. Image: Pat Daly, © Gem-A .

Inclusions are numerous and varied. A few include silk, zircon haloes (circular stress cracks around a zircon crystal), hexagonal and straight colour zoning, feathers (partially healed fractures), negative crystals, two-phase inclusions of a gas and liquid, and fingerprints, which are especially neat feathers.

Read more: Ruby and pink sapphire from Greenland

Generally, the presence of inclusions within a sapphire will make it less valuable, especially if this influences the stone’s overall durability. However in some cases, with Kashmir crystals for instance, the opposite is true. Sapphires sourced in Kashmir, India, often have a very slight milkiness caused by very small inclusions. Colour zoning and stress fractures scatter light to create an almost velvet optical effect without compromising the stone’s transparency. The Kashmir mines are no longer actively mined which adds to the rarity and desirability of this locality.

LocalitiesCommon natural sapphire inclusions
Myanmur
(Burma)

Rutile 'silk', accompanied by pinpoints of rutile. Long needles of apatite; dolomite inclusions (Mogok). Convoluted feathers, silk, hexagonal colour zoning in some stones.

Sri Lanka
(Ceylon)
Crystal inclusions: particularly mica, pyrite and zirca crystals with haloes; healed fractures often resembling fingerprints; rutile 'silk', two-phase inclusions; apatite crystals. Graphite present as solids in two-phase or three-phase inclusions. Elongated negative crystals and pyrite/pyrrhotite are common.
Australia Strong zoning, feldspar, zircon crystals with associated haloes.
Colombia

Crystals of rutile are common.

Table showing common natural sapphire inclusions found in different localities worldwide.
 

Like star rubies, blue and fancy coloured sapphires can display asterism due to silk inclusions. To form a star, corundum needs to have abundant silk inclusions running in three directions at 120 degrees to one another. In order to best display a star, these gems must be cut en-cabochon with the inclusions oriented parallel to the base.

Read more: Exploring Inclusions in a Twelve Point Black Star Sapphire

Light reflects at 90 degrees off of the inclusions to show intersecting, bright bands of light that seem to hover above the surface of the sapphire. Natural star sapphire cabochons are often cut with a slightly rounded base to preserve yield, thereby commanding a higher price.

One of the most famous star sapphires is the greyish-blue Star of India, housed in the American Museum of Natural History in New York. This gemstone is 563 carats and displays a star on both sides, which is atypical.

Read more: The Star of India Sapphire - A Famous Gemstone


An example of a synthetic star sapphire. Image: Pat Daly, © Gem-A .

Sapphire Treatments

Most sapphires on the market today have been heat-treated to improve their colour. These treatments can enhance and deepen a very pale colour or lighten a very dark sapphire.

Another treatment is surface diffusion, which is achieved by heating an already faceted stone in colouring elements, such as iron and titanium, to produce a stronger blue colour that is surface-deep. The stone is then re-polished to sharpen the facet edges. One way to discover this treatment is to place the stone on its table over a diffused white light either directly on the light or immersed in a liquid such as water or baby oil, and to look at the colour concentration.

The location of the colour's presence within the stone can help to determine whether or not it has been treated. For example, if the colour is mainly concentrated at the facet edges and you can see a clear outline of the stone, it has been surface diffusion treated. If the outer edge of the stone fades away and the colour zoning is straight and does not seem to be dictated by its relation to the facet edges, then it has not been surface diffusion treated.

Read more: Understanding the Value of Sapphires

Lead-glass filling is a treatment that can be used to enhance the colour and overall appearance of all varieties of corundum but is more commonly seen in rubies. The lead glass is used to fill surface-reaching cracks and is often an ideal colour such as a saturated red or a vivid dark blue. To detect this treatment, inspect with a loupe to detect fine lines on the surface of the gem (surface-reaching cracks).

Corundum Sapphire Treated Co Glass Filled and Heated GemA PD 0220An example of a lead glass filled sapphire. Image: Pat Daly, © Gem-A.

Look for colour-concentration that is limited to cracks within the stone (a key indicator of this treatment), and if there are bubbles, they will be confined to the glass in the cracks. A red flash may be seen in the glass filling.

Natural Sapphires vs. Synthetic Sapphires

Whilst synthetic stones display an almost identical chemical composition to natural corundum, uncut synthetic specimens can often exhibit a variety of different crystal habits. One of the ways to separate synthetic and natural sapphires is by their characteristic inclusions.

The most common type of synthetic corundum is Verneuil flame-fusion. Verneuil flame-fusion sapphire forms as a boule which is shaped like a bottle. Faceted verneuil flame-fusion sapphires commonly display curved colour zones which are present due to the formation of the rounded boule.

 An example of Verneuil flame-fusion in synthetic corundum, which forms as a boule. Image © Gem-A.

These curved growth zones can be detected with both a loupe and a microscope depending on the size of the stone and the visible depth of colour saturation. Elongated gas bubbles as well as induced 'fire marks' caused by the polishing process may also be seen on the surfaces of the facets. These ‘fire marks’ are typical of corundum polished without sufficient care and are an indication, but not irrefutable proof, that the stone is synthetic.

Additionally, you can use the diffraction grating or prism spectroscope to detect synthetic Verneuil flame-fusion blue sapphires. Whilst many natural blue sapphires show an absorption spectrum of between 1, 2 or 3 black bands that appear in the blue, Verneuil flame-fusion blue sapphires do not show a spectrum whatsoever.

Sapphire Care and Caution

Sapphires have a hardness of 9 on the Mohs scale of hardness, and their ability to resist scratching and wear while taking a bright vitreous polish, not to mention their irrefutable beauty, makes them ideal for everyday wear. For good practice, do not put these gemstones in ultrasonic cleaners and be careful when setting them as they can chip or fracture.

Heat treatments are relatively stable and will not affect the stone’s ability to be cleaned. However, if a sapphire is filled with cobalt-coloured lead glass, that is a totally different story and care must be taken when the stone is cleaned and also when it is taken to a jeweller for setting or jewellery repair. It is crucial that you are aware of this type of treatment as lead glass has a lower melting point than sapphire and will leak out of the stone should it be heated by a jeweller’s torch.

Start your gemmology journey with our range of Short Courses and Workshops.

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Cover image: Synthetic sapphire showing seed crystal inclusions. Image: Pat Daly, © Gem-A.

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How to Separate Natural from Synthetic Ametrine using Conventional Equipment

Guy Lalous ACAM EG summarises the discovery of features that could be used to distinguish between natural and synthetic ametrine from The Journal of Gemmology; from the orientation of growth striations to the interference patterns caused by twinning.

What about natural ametrine?

Ametrine is a bicolored quartz variety that contains both amethyst and citrine zones in the same crystal. The only significant source of natural ametrine is eastern Bolivia’s Anahi mine, where it occurs in veins in a dolomitic limestone. The amethyst-citrine bicoloration results from quartz precipitation at very specific geochemical conditions, temperatures, and growth rates. The combination of amethyst and citrine colours in natural ametrine from the Anahí mine has been attributed to colour zoning that differentiates rhombohedral r (violet) and z (yellow) growth sectors.

The colour of iron-bearing quartz depends on the valence state of the iron. The citrine colour in Bolivian ametrine appears to come from the incorporation of very small aggregates of Fe3+. The amethyst colour develops in two steps. First, individual Fe3+ ions replace Si4+ ions in the quartz structure. To develop the amethyst colour, the crystal must be exposed to ionizing radiation to oxidize the iron in the 4+ state.

Shown in this composite photo are three custom-faceted natural ametrines: a 19.87 ct round StarBrite cut, a 20.35 ct cushion ZigZag cut and a 13.69 ct square StarBrite cut. Courtesy of John Dyer Gems, Edina, Minnesota, USA; photos by Ozzie Campos.

What about FTIR?

FTIR is a technique that measures absorptions within the infrared part of the electromagnetic spectrum. In infrared spectroscopy, IR radiation is passed through a sample. Some of the infrared radiation is absorbed by the sample due to vibrations of molecules in the crystal structure and some of it is transmitted. The resulting spectrum represents a molecular fingerprint of the sample. Infrared spectrometry is very useful to detect impregnations in gemstones (polymers, oils and resin), heat treatment in corundum and to distinguish certain natural and synthetic gem materials. Full width at half maximum is the width of the spectrum curve measured between those points on the y-axis, which are half the maximum amplitude.

What about EDXRF?

X-Ray fluorescence analysis using ED-XRF spectrometers is a commonly used technique for the identification and quantification of elements in a substance.

Beginning in 1994, Russian gem-quality synthetic ametrine entered the market. Synthetic ametrine can be identified by employing advanced techniques, such as EDXRF chemical analysis, and IR spectra. High-resolution (0.5 cm-1) FTIR analysis has shown that a band at 3595 cm-1 is present in the vast majority of natural amethyst. If the 3595 cm-1 band occurs in synthetic amethyst, it has a much larger FWHM (Full width at half maximum) value than in natural specimens. EDXRF chemical analyses revealed higher concentrations of K, Mn, Fe and Zn than in natural ametrine.

What is a conoscope?

The conoscope is a polariscope accessory tool. It is a strongly converging, strain-free glass sphere. When a gemstone is positioned between two crossed polarizers, interference colors that are centered in the specimen will be witnessed with the conoscope when the optic axis is exactly perpendicular to the polarizers.

Previous studies focused on the possibility to separate natural from synthetic ametrine using the refractometer and the polariscope. Quartz is a uniaxial mineral with two unique refractive indexes along its three crystallographic axes. The unique axis is the optic axis. The amethyst-citrine colour boundary in natural ametrine is oriented roughly parallel to the optic axis; in synthetic stones, the boundary is oriented at an oblique angle to the optic axis. The gemmologist needs only to find the direction of the optic axis to determine whether an ametrine is natural or synthetic.

The optic axis in a uniaxial gemstone can be found with a polariscope that has a conoscope lens and, on occasion, with a refractometer. The direction of the optic axis cannot be obtained by refractometer readings for samples cut with their table at random orientation to the optic axis and some difficulties may arise with samples displaying complex colour zoning or twinning.

In this article, the authors explain the possibilities for separating natural from synthetic ametrine by microscopic examination. The immersion microscope was used to look for twinning features, to establish the orientation of the violet/yellow colour boundaries and the direction of growth striations relative to these boundaries, and to observe any characteristic inclusions.

Faceted natural ametrine gemstones from Bolivia typically display only two colour zones, as seen here viewed toward the table facets (top) and toward the pavilions of the same samples (bottom). The stones weigh from 2.45 to 7.45 ct (upper left, 11.7 × 10.8 mm). Photos by K. Schmetzer.

 What are Brewster fringes?

Amethyst from worldwide localities is commonly Brazil-law twinned, which is an intergrowth of right- and left-handed quartz. Such twinning is evidenced only by examination under polarized light. It results in sectors which, when viewed perpendicular to the c-axis, show symmetrical trigonal patterns of dark bands known as Brewster’s fringes. In Bolivian ametrine, these fringes are found only in the alternating amethyst sectors, and not in the citrine sectors.

Between crossed polarizers, the samples show interference patterns (Brewster fringes) that indicate Brazil-law polysynthetic twinning of the violet r growth sectors. Photomicrographs by K. Schmetzer, in immersion.
Optical FeatureNaturalSynthetic
Twinning

Violet growth sectors are intensely twinned on the Brazil law, showing various forms of Brewster fringes with crossed polarizers;
yellow growth sectors are not polysynthetically twinned.

Violet and yellow growth sectors are primarily untwined; small areas within the violet growth
sectors may be twinned on the Dauphiné and/or the Brazil law.

Violet/yellow boundaries Mostly parallel to the c-axis or only slightly inclined to the c-axis (up to about 10°).

Inclined between 20° and 38° to the c-axis.

Growth striations Violet growth sectors: inclined at about 67° or 38° to the violet/ yellow boundary; yellow growth sectors: none observed.

Violet growth sectors: parallel or almost parallel to the violet/ yellow boundary, mostly inclined
at angles between 0° and 8°, with a maximum inclination of 18°; yellow growth sectors: very
weak striations parallel to the basal face.

Fluid inclusions

Rare fluid inclusions, occasionally reflecting the polysynthetic twin pattern of the violet growth zones.

Rare two-phase (liquid and gas) inclusions elongated parallel to the c-axis.

Table showing diagnostic features of natural and synthetic ametrine using immersion microscopy.

The microscopic procedure for identifying these key features can be summarized as follows. The examination of a faceted sample of unknown origin should begin by orienting the dominant colour boundary perpendicular to the rotation axis of the sample holder. If the stone is natural, the typical interference pattern with Brewster fringes will be revealed upon rotation of the sample.

Furthermore, growth striations inclined at relatively large angles to the colour boundary will be observed in the violet portion of the stone after a rotation of about 40° versus the c-axis. If the sample is synthetic, rotating the sample generally will not bring the optic axis into view, and violet growth striations parallel or at a small angle to the violet/yellow colour boundary frequently will be present. It is possible to find the optic axis in a synthetic sample by moving it to other orientations within the sample holder, in which case an untwined interference figure normally will be seen.

In natural ametrine, the colour boundary between the violet r and yellow z growth zones more-or-less follows a prismatic m crystal face but is not exactly planar. In addition, growth striations are present in the violet r sectors, and they are parallel to an external r face and inclined to the violet/yellow boundary. The angle between the growth striations and the colour boundary measures approximately (A) 67° or (B) 38°. Photomicrographs by K. Schmetzer, in immersion.

Separating synthetic ametrine from its natural counterpart using conventional gem lab equipment is possible, provided that the gemmologist has a good understanding of the morphology and optical mineralogy of both natural and synthetic material. The authors insist to use immersion for microscopic observations as the various patterns or structures observed without are of less diagnostic value.

This is a summary of an article that originally appeared in The Journal of Gemmology entitled 'Distinction of Natural and Synthetic Ametrine by Microscopic Examination - A Practical Approach' by Karl Schmetzer 2017/Volume 35/ No. 6 pp. 506-529

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: Crystal clusters that occupy the storage room of the company Minerales y Metales del Oriente in Santa Cruz, Bolivia. Only small portions of the crystals are of facetable quality. Photo taken in 1997; courtesy of Udo Reimann.


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Speaker in the Spotlight: Q&A with Patrick Dreher

Master Carver, member of the Board of Trustees of the German Gemstone Museum and board member of the Federal Association of the Gemstone and Diamond Industry, Patrick Dreher is one of the highly anticipated speakers at the Gem-A Conference 2017 not to be missed.

Within his lecture on ‘Generations of Mastery’, Patrick Dreher will be delving into the history of Idar-Oberstein and why the town gets its reputation as a gemstone metropole. Patrick will take attendees back in history, exploring the generational legacy of the Dreher family as well as exploring how an animal carving is produced.

Gem-A caught up with Patrick Dreher to secure some exclusive insider knowledge and to find out what inspired him to pursue a career in master carving...

Q. How, when and what originally inspired you to pursue a career in carving?

I grew up in a gemstone carver family with a very long tradition working with gemstones; the history of my family goes back 13 generations. The first generation were agate cutters and the last 5 generations have been gemstone carvers. So it was more or less clear that I would follow in our family business. For me it was an easy decision to go this way, because I like nature, animals and even more so, gemstones. When I was younger I would often watch my father working, fascinated. After my first carving experience as a young child, I was sure I wanted to go on in the profession.

Q. Where do you find inspiration for your commissioned carvings?

Nature and animals themselves are the best inspiration for our art objects. Gemstones also often “tell” us what they want to be or become. It sounds a little funny; how can a stone tell you what it wants to be? Before we start one of our art objects, we look for the right gemstone and examine its features. We get to observe the stone, formulate an idea and analyse what will be the best “use” for the stone and what animal wants to come out of the stone. With expensive stones like aquamarine, we have to take care that not too much is cut from the stone. We try to keep these gemstones as big as possible in terms of their dimension and weight.

Multicolour tourmaline toad, ©Bill Larson. Photo by Robert Weldon.

Q. In your presentation at this year’s Gem-A Conference, what should we expect to hear and learn from you?

I will be presenting a lecture concerning the history of Idar-Oberstein and my family. The focus upon these subjects will be the shortest in my lecture; it will only be a brief overlook. The second half of my lecture will demonstrate to visitors how a gemstone carving is produced. I want to show them the step by step motions from start to finish whilst explaining the most important steps. The final part of my lecture will consist of a slide show showcasing a variety of finished carvings we have produced in the last year.

Q. What one word or phrase would you use to describe both yourself and the mission of your work?

“The passion” for gemstones and wildlife. The combination of beauty found within gemstones, mother earth alongside the living beauty of animals.

Strawberry starfish ©Bill Larson. Photo by Robert Weldon.
  • 'Generations of Mastery’ by Patrick Dreher will take place Sunday 5 November 2017 at 09:45 - 10:45am.
  • To purchase your tickets to the Gem-A Conference 2017 and full listings of the programme, please visit the official website here.

 

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 Patrick Dreher and Silverback Gorilla ©Dreher family. Strawberry starfish and tourmaline toad, ©Bill Larson. Photos by Robert Weldon.


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