Belinda Morris talks to renowned and much-admired lapidary John Dyer, one of the speakers at the 2016 Gem-A Conference, about the science and art of gem cutting. 

Did you train as a gemmologist or gem cutter?

I loved gems and business from an early age. I was also home-schooled and one of my parents’ strategies for teaching me was to purchase books on subjects I was interested in, so they bought books on gems and gemmology for me (Gem Identification Made Easy by Antoinette Matlins and Antonio C. Bonanno was one of the first) and that stoked my interest.

At 16 I wanted to start in the gem business and my dad said he would help me out. One thing led to another and we ended up going to Zambia to buy gemstones. We bought rough gems instead of cut ones to get a better deal and when we brought them back we took them to a cutter to have them cut. He did a really bad job on them and charged us a lot of money for it. 

This resulted in us getting mad and buying a faceting machine because, as my father said: “We can do that well, or better, ourselves, and cheaper too!” This all turned out to be a blessing in disguise because it helped us to discover that I love to cut gems. So although the gems we bought on that trip were not super profitable in the end, it started us in the direction of what has now become the focus of our business - high quality and creative gem-cutting. 

I never had any formal training. There were no lapidaries interested in teaching near me that I knew of, and as far as gemmology goes I mainly learned from books and practical experience. I would consider myself a far better cutter than gemmologist, but I do have certain practical, applicable gemmological techniques which help me when purchasing rough. Rough is almost easier to ID than cut gems, because you often still have the crystal habit, visible cleavage planes and more inclusions and other factors to help identify a gem and potential treatments it may have undergone. 

Does the stone influence your design or do you choose the stone based on a particular cutting style that you want to see? 

The shape, colour and clarity of the rough are the main considerations in choosing the cut I am going to do. Usually I buy the best rough I can find and then cut to what I feel is best suited to it. There are times when I don’t buy a piece because I feel the shape and size it could cut would not have good marketable appeal, but other than that I pretty much let the rough dictate to me what it wants to be (that’s within certain limitations of marketability and visual appeal, of course). 

That challenge that each gem represents - trying to bring out its maximum potential - is one of the things I most enjoy about cutting. There are so many considerations that go into it and for the most part all those decisions are made on the fly as I saw and preform (pre-shape) the gem for dopping and faceting or carving. 

What is your favourite stone to work with and do you have a preferred design for it? 

My favourite gem to work with is aquamarine since it comes in reasonably large and clean gems, is easy to polish and has great transparency so it is well suited to a wide variety of different cutting styles. Also, since it isn’t dark, it shows the cut well instead of hiding it like some extra dark gems do. 

There are sometimes cutting styles I prefer for specific gems; those with high dispersion (e.g. zircon) do better with flat faceted cuts than with concave facets or carving, since those tend to reduce the dispersion. Other gems with low dispersion I love to cut with concave facets or carving styles since they can increase the brilliance. It’s all part of the decision making process when deciding what to cut a specific piece or rough into. 

You use many less well-known gemstones, do you find that this increases the public’s awareness of these stones, highlighting how beautiful they can be?

As far as using ‘less well-known’ gems go I find that the market is much more accepting of a wide range of gems than in the past. TV shopping has introduced many strange gem types to a large public audience and a certain percentage of that public has gone on to learn a lot about gems and become educated and sophisticated buyers. This, coupled with how expensive the ‘traditional’ gems have become, has really opened a wide door to the lesser known gems. 

That being said though, most of the gems I cut are still within the parameters of what is familiar to most jewellers - aquamarine, beryl, morganite, citrine, amethyst, ametrine, garnet of all kinds, sapphires, emerald, ruby, peridot, tourmaline (all colours), spinel and zircon make up most of my inventory.

Sometimes I will do a very rare gem, such as bicolour spessartite, phenakite, oligoclase or similar, but they are the exception rather than the rule.

What do you endeavour to reveal in stones? 

Essentially what I am looking to reveal is the full potential for beauty that is in each piece of rough. So much labour goes into the searching for and mining of gem rough that I feel it should be cut in a manner that respects its true rarity and uniqueness. But at the same time some sacrifices of size and weight will need to be made for the gem to achieve its maximum beauty. That is the goal that I aim for. 

What do you look for when selecting a piece of rough? 

When selecting rough I look at the size, shape and clarity of each piece. I also take into account the value of the finished piece because there is a lot of labour involved in our cutting and if the finished value of the gem is too low we will not recoup our labour costs. For that reason there are some pieces of rough that are cool and pretty but I just can’t buy them because they won’t generate a profit. 

Do you travel to mines around the world to procure your own rough or do you often buy at shows? 

I have travelled to various countries in search of gems. My most valuable gem (my wife) is Brazilian from the state of Paraíba so the search has paid off! However, gems are often found in very small quantities and a trip direct to the mines can be a fruitless affair since there might not be any production for months at a time. This often results in my needing to buy from middlemen of some kind. Over the years we have formed relationships with a number of rough suppliers who bring us a variety of rough, that it would have been very hard to have access to on our own. After all, cutting is a time consuming business and if I spent all my time running about after rough I wouldn’t get much cutting done. 

Have you had any major cutting catastrophes? 

Major cutting catastrophes are something you like to put out of your mind, but there have been a number of them over the years. There was the kilo of pink tourmaline rough we heated without grinding clean first and broke almost all of it. There was a bixbite (red beryl) from Utah that cost us thousands of that we hoped to get over a carat’s worth of finished cut stone out of it, but it shattered due to internal stress and we ended up with three very small gems from it. There was the imperial topaz that I was carving and got too hot and broke it in half… and many other gems that have broken during carving, or been chipped or something similar. Over 20 plus years of cutting there are a lot of things like that which happen.

Talk us through the process of one of your famous cuts such as the Super Trillion™. What’s the process of cutting a gem in this way? How long does it take to cut some of your most famous designs?? 

The Super Trillion™ is all flat faceted and is an adaptation of a cut that was explained to me by Chris Remen (now deceased) which over time I tweaked to make a number of improvements to. The result is a semi-traditional looking trillion which I feel is super. Since it has so many facets it is very time-consuming to cut. How long it takes depends completely on the type of material and the size of the gem but it usually takes a day or longer to complete. 

A 26.11 ct Citrine Super Trillion^TM. Photo by John Dyer

Do you have any advice for people who want to take up lapidary? 

To take up lapidary as a hobby, the best thing to do is search for a local lapidary club. Often there will be retired members who will teach cutting for a very reasonable price and this often allows you to avoid the initial relatively high cost of the machinery and supplies. For those who want to make this a profession, I would recommend studying the market to be sure that it is really what they want to do… because it is not the easiest thing to make money at. 

You need to be a skilled cutter (something that often takes five years or more to accomplish) and make large investments in raw materials if you are going to sell your own gems. If you don’t sell your own gems, you are going to need to find a niche market for your cutting services and be very fast if you expect to make money because much of the gem trade is used to Asian pricing on gem cutting and that is hard to compete against until you educate your clientele about the difference in look and quality. That means a lot of outreach and marketing is involved. 

You’ve won many awards for your work; which means the most to you? 

The award that means the most to me is the first place I took recently at the German Award for Jewellery and Precious Stones Idar-Oberstein 2015. This is one of my favourite competitions, but the fact that you have to adhere to a theme makes it more complicated. You might have a perfectly beautiful idea for a gemstone cut, but it must go with the theme to win. The theme in 2015 was ‘Light My Fire’, so I thought that an orange gem would fit well with the idea of fire. With this in mind, I searched through my stock of rough and selected a deep orange citrine, which, once ground clean, was a flame shape. Despite this it was still a challenge to decide what to do with the underside of the gem to make it look like fire. However, an idea came to me to execute a pattern that I had never done or seen before and which required an adaptation of my existing machinery and techniques - the result is a gem with a flame shape, but which also has little flame-shaped internal facets on the back which reflect light individually with varying intensities so that they look like flames shooting upwards as the gem is moved. 

Where do you see yourself going with your talent? What’s next for you in the lapidary world? 

It might not be super romantic, but I guess what I see is gradually improving what I already do and adding new styles and techniques to that. As a result of this I feel that each year our gems are better cut, more beautiful and more saleable. ■   

To view John Dyer's work click here

This article originally appeared in Gems&Jewellery Sept/Oct 2016 / Volume 25 / No. 5 pp. 28-32

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.

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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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This article by Guy Lalous ACAM EG digests a technical article from The Journal of Gemmology and discusses the capabilities of Laser Ablation Inductively Coupled Plasma Time-of-Flight Mass Spectrometry (LA-ICP-TOF-MS) compared to conventional Inductively Coupled Plasma Quadrupole Mass Spectrometry (ICP-Q-MS). Potential applications of this new analytical technique are also described.  

Gem testing has evolved into an advanced materials science using sophisticated instrumental technologies for detailed chemical and structural analyses. The chemical analysis of gem materials allows identification of synthetics and treatments. Trace-element analysis is useful to identify the geographical origin of high-end stones. When the origin of a stone has a significant impact on it’s value, the cost associated with this technique may be  justified.

How does LA-ICP-MS work?

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

What is LA-ICP-MS used for?

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

What is ICP-Q-MS?

There are multiple varieties of ICP-MS instruments, which use different mass-separation schemes in analysis. Of these the ICP-Q-MS, which uses a quadrupole is the most popular. The quadrupole is a mass filter. The quadrupole consists of four cylindrical rods arranged so that the ionised sample travels down the centre. Depending on the electro-magnetic field of the rods, the trajectory of the ionised particles is affected, with selected ionic weights based on the m/Q being filtered out and the ions of interest reaching the MS detector. The ability to filter ions on their m/Q allows ICP-MS to supply isotopic information. Different isotopes of the same element have different masses.

What are the limitations of ICP-Q-MS?

The user of this technique has to define a preselected list of isotopes. Isotopes are sequentially measured one at a time, the ‘limited’ sample volume is divided (segmented) between all measured isotopes, thereby drastically reducing the effective sensitivity if many isotopes are monitored.

What are the capabilities of ICP-TOF-MS?

ICP-TOF-MS is one of the latest and most advanced technologies in the ICP-MS family. Time-Of-Flight (TOF) uses the principle that the ‘flight’ duration for one ion passing through a fixed flight tube is related to its m/Q.  Lighter ions take less time to travel the same distance compared to their heavier counterparts with the same charge, provided they have identical kinetic energy, therefore achieving mass separation. ICP-TOF-MS acquires spectra from the lightest to the heaviest isotopes at a higher speed as well as achieving a better resolving power than conventional Q-MS. It ‘snaps pictures’ of the full and continuous mass spectrum without the need to assign isotopes of interest. Such a spectrum reveals almost the full elemental composition, reaping the benefits of the robust plasma source and there is no need to re-ablate the stone due to an incomplete or ‘badly’ chosen predefined list of isotopes.

What practicalities are there to consider with ICP-TOF-MS?

Due to technical limitations the ICP-TOF-MS model described in this article cannot measure light isotopes while maintaining a high sensitivity for heavy isotopes. It takes two measurements to complete the full elemental analysis from Lithium to Uranium. Limit of detection (LOD) values range from single-digit parts per billion (ppb) for heavy elements to low parts per million (ppm) for light elements. TOF-MS provides better LOD than Q-MS. TOF-MS collects all information in the full mass spectrum with no information loss.

What are the potential applications?

The possibilities of the technique will enhance applications such as trace-element characterisation of gemstones and pearls for origin determination and treatment detection, and will open new research opportunities for age dating, inclusion studies and high-spatial-resolution chemical mapping of gems.

The new instrument is called GemTOF and was installed at SSEF in July 2016. ■  

To find out more information about this exciting technique visit GemTOF

This is a summary of an article that originally appeared in The Journal of Gemmology entitled ‘Simultaneous High Sensitivity Trace-Element and Isotopic Analysis of Gemstones Using Laser Ablation Inductively Coupled Plasma Time-of-Flight Mass Spectrometry’ by Hao A.O. Wang, Michael S. Krzemnicki, Jean-Pierre Chalain, Pierre Lefèvre, Wei Zhou and Laurent E. Cartier 2016 / Volume 35 / No. 3 pp. 212-222

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.

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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

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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

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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

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Download PDF of Volume 35 / Issue 4 / 2016

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Point Point Point Point

Award-winning photographer Danny Sanchez GG, a speaker at the 2016 Gem-A Conference, reveals the secrets of photomicrography, the equipment he swears by and his favourite gemstones to photograph.

Q. What drew you towards photomicrography?

I was a working musician in Los Angeles and wanted a change of pace. I’d always loved gems and minerals and when I discovered that you could study them, their origins and applications, at the Gemological Institute of America, I couldn’t enrol quickly enough. The day I opened the course material and saw an inclusion photomicrograph, I was hooked.  

Q. What special equipment do you use?

I might be a little biased so I feel like a lot of my equipment is special. I think my most unusual piece of equipment is a vertical stepping rig that moves the microscope mere microns at a time.  

Q. Can you explain stacking for those that don’t know?

Microscopy deals in very narrow focal planes. A single photo has very little that is actually ‘in focus’. Focus stacking is a technique that allows one to merge multiple photos, each with different focal planes, into a single photo with greater depth of field. This is stacking. Using this technique, one is able to ‘manufacture’ depth. There is definitely a way to overuse stacking. Besides the visual residue that can be found in some photo ‘stacks’ (a group of photos merged into one), if a photo is rendered with too much depth, the viewer can lose perspective. Simply put, but somewhat counterintuitively, a photo with too much depth can look flat. 

Left: A single photomicrograph play of colour in opal from Jalisco, Mexico. Field of view 3.05 mm. Right: The complete stack of 81 photos. Field of view 3.05 mm

Q. Do you look at images from earlier and wish you could retake some of the spectacular ones to add the ‘dimension’ it offers?

I definitely understand the impulse to go back and re-do a shot, but it’s not a strong one for me. I’m always trying to look forward, and to reproduce or re-tool an image I’ve already made seems like a step backward — particularly in light of how many dynamic subjects this industry offers. (For more information on stacking see Prince, N., ‘Use of Stacking Software for Expanding Depth-of-Field in Inclusion Photomicrography’, The Journal of Gemmology, 2014, 34(3), 188–89).  

Q. Do you have any advice for gemmologists wishing to try photomicrography at home?  

There are an overwhelming number of details to consider when trying to take a successful photograph through the microscope, and it’s hard to see the forest for the trees. The simplest recommendation I can make is: buy more light than is necessary. Gemmologists are used to using a specific type and amount of light during observation and imagine that will be sufficient when they sit down to take a photograph. It never is. Light is everything in photography; it’s even more important in photomicrography.  

Q. Do you have any particular favourite inclusions or gemstones to photograph?  

This past year I’ve immersed myself in opal with matrix. I have yet to find a mineral more dynamic that so readily yields actual landscapes. Part of what I look for in my own work is the feeling of being transported somewhere ‘other’. I enjoy the challenge of finding that in quartz or corundum, but when I work with opal in matrix, it’s almost like the photo takes itself.   

Q. How do the public react to your photos? 

Most (non-gemmological) people don’t know what they’re looking at when standing in front of my photos. Once I tell them that it’s a photo of the inside of a gemstone, more often than not, they don’t believe me. Finally, when they do, they have a million questions. It’s really great to see people so invigorated about gems and minerals. I’m sure they’re much more interested when they leave than before they arrived. 

Q. How do you source the stones that you work with? 

Mostly, I’ll buy at trade shows, looking through dealers’ back stock inventory — stones that, for one reason or another, have been passed over. Part of the joy of my process is these little discoveries and bringing something out of them that no one could have imagined. There’s something about owning the stones I work with (and hopefully producing an image from them) that makes the final product that much more satisfying. I’m not sure I can satisfactorily articulate why. Maybe, like every other gemmologist, I just like to hoard stones. 

Q. Do you see your photos as an educational tool or as an art form? 

Art is an inherently selfish act and mine is certainly no exception. All I ever wanted was to capture in my images a sense of mystery and wonder. It is purely self-serving and in this regard, it’s very ‘artsy’. But when people look at my images and discover that they are photos of actual minerals inside other minerals, there is an immediate spark of curiosity. The moment that happens, my photos become educational. 

Q. How long does it take you to capture the ‘magic’ shot? 

I’ll sit down with a parcel of stones and spend hours turning them over in my hands, changing the lighting environment, trying my best to disappear into the process. Once I’ve decided on which stone I’ll pursue, it could take another hour or so to test shoot dozens of lighting environments. The shooting and processing of a stack of 100 or more photos takes another 30 to 40 minutes. The real work happens over the following several days while I digitally develop the photo, just as I would if I were working in a traditional darkroom. 

Q. What’s the most frustrating thing about photomicrography? 

The most frustrating thing is that I can’t do it for a living. My photos don’t have to be perfect, but they have to be representative of the view through my oculars, at the same time capturing the feeling of the moment of discovery. If I don’t feel I’ve done that after I’ve gone through the process of taking the shot(s) and developing the stack, it can be very frustrating. 

Q. What are your future plans for your work? 

Most of my work for the past few years has focused on atmosphere, the space within the stone and not any particular inclusion or the capturing of inclusions. That’s what interests me the most and that’s what I see myself pursuing; capturing and creating the space within gems. 

Q. If fleeing a burning building, what equipment do you grab?

Luckily for me, I’m not a photographer in the traditional sense of the word. I didn’t grow up aspiring to take photos nor did my penchant for gadgetry lean in that direction. My entry into the world of ‘prosumer’ cameras and lenses began with photomicrography. Because of this, I don’t have a collection of lenses or cameras that would make it hard to choose if fleeing a burning building. My most crucial pieces of equipment fit into one small hard case. I’m definitely fortunate in that regard. 

Q. Your studio improvisations suggest you have a good eye for engineering solutions to suit your needs…

Everything I have done, I’ve done on the shoulders of others. Of course, I’d like to think of myself as a tinkerer and problem solver but most of my equipment has existed in some form, on someone else’s desk, in someone else’s setup. It wasn’t easy piecing it all together but with help from a very small handful of people from around the globe, I’ve put together something that I’m really proud of. 

Q. Another big part of the job these days is software; how do you select the software you use? 

I’ve mentioned the stacking software and while that’s a tricky nuanced piece of software, it performs one function and is therefore finite in its ability to affect a photograph. Beyond that there is developing software such as Lightroom and Photoshop. Together, they can be used to alter an image in infinite ways. While they are indispensable tools, I try to remain as faithful to the view through my oculars as possible. 

Q. What are the ‘frontiers’ to be explored in photomicrography? 

I think the frontiers of photomicrography lay in the direction of software. We’re so lucky to be living in a time of amazing advances, in what computers can do to aid in our perception of the world around us. One day I hope to be able to pop on a pair of VR glasses and take a flight through a Kashmir sapphire or Mexican opal. 

Q. Do you have any gemmological heroes? 

Of course, Eduard Gübelin and John Koivula. Without their work, who knows where I’d be. 

Q. Who first encouraged you to be a photographer? 

In 2007, a year or so after I bought my first microscope, I was working at a trade show and was introduced to Edward Boehm. I already knew who he was, both in the trade and his family’s importance in gemmology. I shook his hand and told him, with no small amount of youthful hubris, that I was going to be a photomicrographer. He flashed me that great smile and told me to go for it. Every subsequent time I ran into him, he would always ask how it was going and if I’d made any progress with my photos. I was the smallest blip in his periphery but for the next five years he never forgot to ask about my photos. During that time I struggled with the pursuit itself and a lot of self-doubt. It wasn’t until 2013 that I was proud enough of my work to share it with the general public. His polite consideration was such a small gesture but it made me think: if this great gemmologist, grandson of the man who helped pioneer this field, hasn’t forgotten about me and my pursuit, I can’t forget either. ■   

To view more of Danny Sanchez's work click here or visit his Instagram @mineralien

This article originally appeared in Gems&Jewellery May/June 2016 / Volume 25 / No. 3 pp. 10-12

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 Opal, from Jalisco, Mexico. Field of view 3.05 mm. All images courtesy of Danny Sanchez. 

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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

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

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

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

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

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

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

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 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

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

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Andrew Fellows FGA DGA takes a look some of the myths and legends associated with one of the world’s most famous gem collections, the Crown Jewels of the United Kingdom.

Foundations were laid for the Tower of London - where the famous Crown Jewels are housed - as early as 1066 by William the Conqueror. Successive monarchs then added to and reinforced the Tower, until, by the late thirteenth century, the general layout seen today was established. The Crown Jewels, the only working collection in Europe, is comprised of over 141 objects, which have been stored securely within the Tower for hundreds of years. It is these that attract hordes of tourists each year.

However, whilst the collection is worth seeing simply for the sheer beauty of the pieces, it is also worth seeing to learn about the captivating stories and histories behind some of the gems.

The Crown Jewels: The Imperial State Crown

The Imperial State Crown - possibly the most well-known individual piece of regalia in the collection - is worn by the monarch at the end of his or her coronation ceremony, and is also used for the State Opening of Parliament. The Crown is such an important piece that it even has its own coach for these important occasions - one that is every bit as ornate as the crown itself. Weighing in at an impressive 3.17 kg, it can only be worn for short periods.

One story says that when George IV was crowned in 1821, he developed a toothache that he blamed on the weight of the crown! The crown contains some of the most important jewels in the Royal Collection, many of which also have the most interesting stories attached to them.

The Crown Jewels: Black Prince's Ruby

One story that most gemmologists are familiar with is that of the Black Prince's Ruby. This is simultaneously one of the most beautiful and most sinister stones… and one which is also completely misnamed. Although referred to as ruby, this is actually a very large gem-quality red spinel, presented to Edward of Woodstock, a fourteenth century Prince of Wales, Duke of Cornwall, and Prince of Aquitaine, referred to more often as ‘The Black Prince’.

The gem, which sits in the cross pattée above the Cullinan II at the front of the crown, has a very dark and bloody history. It was first recorded in the fourteenth century as being owned by a Moorish Prince, Abu Said, who attempted to surrender to the conquering forces of Pedro the Cruel. Abu Said was ambushed under a flag of truce and executed with this large spinel being taken from his corpse.

This was just the start of the trail of blood, as Pedro himself broke several contracts, before presenting the stone to Prince Edward as a down payment for military assistance. The remainder of the payment was supposed to consist of treasure and jewels, but was never delivered, and eventually Pedro himself was ambushed and stabbed to death by his half-brother.

Read more: Last chance to see the record-breaking Foxfire Diamond at the Smithsonian

The stone was later worn in the battle helmet of Henry V when he went into the Battle of Agincourt in 1415, and allegedly saved his life when he received a blow to the head from an axe - one which destroyed the helmet, but didn't kill Henry. The 'ruby' was recovered from the shattered helmet and remained with Henry V until his death.

The same unfortunately cannot be said of Richard III, who also wore the 'ruby' in his battle helmet when he fought at the Battle of Bosworth Field in 1485. Presumably, Richard thought it would protect him and bring him luck, but sadly he was mistaken and died on the battlefield. This same ruby was later used in the crowns of Henry VI, Edward IV and Henry VIII (who wore it in a collar), before being sold by Charles I. It was returned to the monarchy for the crown of Charles II, and was subsequently used for the coronation of George IV.

The Crown Jewels: St Edward's Sapphire

Also in the Imperial State Crown is a sapphire, set in the cross on top of the Crown. Legend has it that this sapphire once resided in the coronation ring of Edward the Confessor, and that one evening he was passing through Westminster when he happened upon a beggar. Having already given away all the money he had on him, he gave the ring to the beggar and thought nothing further of it.

Read more: The history of diamonds in engagement rings

Years later two Englishmen were on a pilgrimage to the Holy Land and, in the middle of a violent storm, saw an old man approaching them. When the old man heard that the two men were English, and that Edward was still King, the old man offered them shelter for the night. When they departed the next morning, the old man revealed himself to be John the Evangelist, and told them that years ago King Edward had given him a ring, which he still had, and gave it to them to return to the King, with a message that he, John, would see the King in Paradise as a reward for his kindness in six months' time.

When the two men returned to England, they gave both the ring and the message to King Edward, who immediately prepared for his death. The King died six months later, to be buried with the ring on his finger. Stranger still is the fact that when the tomb was reopened in the twelfth century, the ring was found on a perfectly preserved corpse.

Whilst some of these stories are merely legend and may or may not be true, what is known as fact is that the Crown Jewels contain some of the best known and largest diamonds in the world, the most famous of which are probably the Koh-i-Noor and the Cullinan.

The Crown Jewels: Cullinan Diamond

The Cullinan was found at the Premier Mine in South Africa, on the afternoon of 26 January 1905, by the mine superintendent, Captain Frederick Wells. Initially he doubted it was a diamond as it weighed 3106 ct and measured 3 7/8 × 2 1/4 × 2 5/8 inches, well over twice the size of any other diamond found to that date.

This was sold to the Transvaal government for £150,000, and two years later the still uncut diamond was presented to King Edward VII on his 66th birthday. Cutting of the stone was a job given to I. J. Asscher and Company, of Amsterdam, who had some experience of cutting large diamonds, although nothing on this scale or value. After three months of consideration, the Cullinan was ready to be cut.

In those days the only way to divide a diamond was by cleaving it - effectively 'hitting' the stone in precise directions to cause the diamond to part along weaker directions, but this had to be done carefully, in order to avoid shattering it. Careful cleaving resulted in nine major 'pieces', and 96 offcuts. Once the whole cutting process was completed, a total of 1063 ct remained.

Read more: Harrods unearths 228.31 ct diamond from its vaults for private sale

The nine major stones, named Cullinan I to Cullinan IX, all reside in the Royal Collection. The majority are set in such a way as to be interchangeable into other pieces of jewellery. Cullinan I, also known as the Star of Africa, is in the Royal Sceptre, and weighs just over 503 ct, making it the largest colourless pearcut diamond in the world.

The Cullinan II (the 'Lesser Star of Africa'), is the largest cushioncut diamond in the world, weighing 317 ct, and is set into the front of the Imperial State Crown. It also has two platinum loops on its setting, so that it can be removed and worn alone, as a brooch or pendant, or with the Cullinan I accompanying it.

The Crown Jewels: Koh-i-Noor Diamond

A second notable diamond exists in the Queen Mother's Crown, this being the Koh-i-Noor, which translates as 'Mountain of Light'. This impressive diamond currently weighs 105.6 ct, having been recut from its original 186 ct for Queen Victoria in 1852.

There is a legend that this stone will bring good luck to any woman who wears it, but a curse to any man! It is said that in 1739 Nadir Shah of Persia conquered the Mogul region, but could find no sign of this rare and fabled diamond, said to be held by the rulers, until one member of the royal court told him of the stone's location. Shah then threw a celebration, and offered to exchange turbans with the conquered leaders as a show of everlasting friendship, knowing that this was the hiding place of the Koh-i-Noor.

The diamond changed hands many times over the coming decades, until in 1850, the Koh-i-Noor finally found its way to England and to Queen Victoria, where it has remained ever since.

Whilst the Crown Jewels are a wonderful piece of English history, they are also shrouded in legend, and are more than just adornments. There are a multitude of stories and histories, all waiting for visitors to uncover. Whether you appreciate them from a gemmological or historical perspective, or simply want to see jewels that most of us will never afford, the Crown Jewels are the perfect way to spend a day in London. ■ 

This article originally appeared in Gems&Jewellery Sept/Oct 2016 / Volume 25 / No. 5 pp. 14-15

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 nine major uncut stones split from the rough Cullinan diamond in order of size (largest to smallest).

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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

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

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

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

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

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

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

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 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

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

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This article by Guy Lalous ACAM EG summarises a technical article from The Journal of Gemmology discussing the identification criteria for early (pre 2009) and current (post 2009) reconstructed amber, based on documented samples at the National Gemstone Testing Center (NGTC) in Beijing.

Newer amber material presents a serious identification challenge for gemmological laboratories. By comparing the structure of reconstructed amber with that of natural amber, is it possible to identify it? 

Read more: Diving into the World of New Zealand Paua Shells

Amber is formed from fossilised tree resin, but may have inclusions of animals, insects, plant debris, minerals, liquids and gases. The fossilisation process involves a progressive oxidation, where the original organic compounds gains oxygen, and polymerisation, which is an addition reaction where two or more molecules join together. This process produces oxygenated hydrocarbons, which are organic compounds made of oxygen, carbon and hydrogen atoms.

What is reconstructed amber?

Reconstructed amber consists of small amber fragments or scraps that have been reformed into larger pieces under heat and pressure. It is commonly manufactured from pieces of Baltic material. According to the process used, two main types of reconstructed amber exist:

Type 1 made without the addition of any substances to the amber fragments.

Type 2 which contains foreign substances (e.g. natural or artificial resins) that are added to make the material more solid and durable.  

What is Baltic amber? 

Baltic amber is fossil resin from coniferous trees. Baltic amber, also called succinate, contains 3-8% succinic acid. It was formed about 44 million years ago and today it is found in forests in Lithuania, Russia and Poland, where it is mined and exported in large quantities. The origin is confirmed by the presence of a ‘Baltic Shoulder’ in the fourier transform infrared spectroscopy (FTIR) spectra. Infra-red (IR) spectroscopy is the most effective scientific method for identifying fossil resins. 

What are the identification features of heated amber?

Heat-enhanced amber contains brownish flow lines. These flow lines result from the oxidation of pre-existing cracks that are healed during enhancement at low temperature and pressure, to solidify the raw material and to help avoid future cracking. The heating process will change the refractive index (RI) and infrared spectral readings. The higher the temperature used, the higher the RI will be, up to a maximum of 1.60. Exposure to greater temperatures may also alter some of the FTIR features: the ~1735 cm⁻¹ absorption band shifts to down to 1716 cm⁻¹, and the ~1157 cm⁻¹ absorption band moves up to 1175 cm⁻¹. The variations in RI and infrared spectra indicate that an amber specimen has been heated, but they do not provide conclusive evidence of reconstruction. 

Read more: Getting to Grips with GemTof Technology

When there is little or no foreign substance present, the FTIR spectra of reconstructed amber looks almost identical to that of natural amber, and additional examinations using a microscope, polariscope and UV lamp should be performed to make the proper identification. Most samples encountered at NGTC are type 1 reconstructed amber.  

What are the identification features of early reconstructed amber? 

Early reconstructed amber involved the use of relatively high temperature and pressure conditions in air. It is relatively easy to identify. The material displays a relatively dark body colour, poor transparency with a muddy-looking interior, and a diagnostic fragmental or mosaic structure (known as ‘blood streak’ in Chinese as it resembles blood vessels). The boundaries between fragments have oxidised (darker) edges that appear translucent brown or red. In addition to this some early-stage reconstructed amber may display uneven surface lustre, due to different hardness characteristics of the partially melted amber fragments.  

A 3-D mosaic structure in early reconstructed amber shows a network of angular boundaries that completely enclose the fragments. Below: By contrast, heat-enhanced amber displays brownish red flow lines that do not interconnect. Magnification 10x

How can you differentiate between natural and reconstructed amber?

Natural amber is amorphous and often shows anomalous double refraction in the polariscope, sometimes displaying snake-like, wavy or patchy extinction patterns. By contrast, early-stage reconstructed amber shows patchy grainy extinction, with clear grain boundaries and often exhibits interference colours. 

Natural amber usually displays even fluorescence, viewed with a UV lamp or in a DiamondView instrument. While darker-coloured early-stage reconstructed amber may not show diagnostic fluorescence, pale-coloured material commonly shows uneven luminescence with a fragmental or granular structure.  

What are the identification features of current-stage reconstructed amber?

Current-stage reconstructed amber is manufactured under relatively higher temperature and pressure in an oxygen-free environment. It is often subjected to post-processing treatments that are designed to conceal identifying features. These include inducing internal and surface cracks (by heating and cooling), polishing with coarse grit to create a matt appearance, darkening the surface colour (by baking), carving complex patterns and applying coloured coatings. Microscopic observation reveals that finer grains are typically used as raw material for current reconstructed amber. Usually showing a more subtle and fine-grained fragmental structure consisting of areas of pale colour are enclosed by dot-like edges. The dark-coloured grain boundaries are nearly absent and can only be seen with careful observation, the ‘blood streak’ structure is not apparent. The post processing treatments obscure the features observed with the polariscope, UV lamp or the DiamondView. 

Above: Viewed with a strong transmitted light source, this opaque reconstructed amber bead exhibits no ‘blood streak’ structure, although the angular fragments are still apparent. Below: Two beads in an amber bracelet consist of natural amber (left) and current reconstructed amber (right) display fuzzy grain boundaries with no ‘blood streak’ structure. The presence of small grains with angular boundaries is the key identification factor for the reconstructed amber bead. Magnification 16x (left) and 12.5x (right)

Conclusion

The most effective method to identify reconstructed amber from natural amber is microscopy, to observe the internal microstructure. The Polariscope and UV Fluorescence are useful auxiliary methods but cannot be used to reliably separate current reconstructed natural amber. ■

This is a summary of an article that originally appeared in The Journal of Gemmology entitled ‘Identification of Reconstructed Amber from Different Periods’ by Haibo Li, Jie Liang, Taijin Lu, Jun Zhang and Jun Zhou 2016/Volume 35/ No. 4 pp. 320-328

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 Flanky internal cracks, eviddence of post processing heat treatment in current reconstructed amber. All photos by H. Li

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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

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

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

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

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

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

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

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 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

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

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Claire Mitchell FGA DGA takes a hands-on look at the Oceanview Mine, in the Pala mining district in California, USA.

Oceanview Mine is situated 2.5 miles northeast of Pala, on the northeastern slope of Chief Mountain, a short, scenic drive from Pala, California. Visitors to the area pass through landscapes bedecked with nurseries growing a multitude of produce and plants; turning off the main highway you pass through beautiful orange groves, finally reaching the dirt track which takes you up to the mine. 

Famous mines in this area also include the Tourmaline Queen, famous for its 'blue cap pocket' tourmaline, and Pala Chief Mine, famous for its kunzite. The area has been a source of gem materials since the 1870s; with its most active period being between 1900 and 1922. 

Claim was first made to the Oceanview deposit in 1907 by Frank A. Salmons. Since then, ownership has passed through several hands during its lifetime, and the mine is now owned by Jeff Swanger, who acts as CEO, owner and operator of Oceanview Gem Mine LLC. In its lifetime the mine has produced some of the best morganite specimens ever recovered in North America, as well as exceptional tourmaline and kunzite, with additional minerals of lepidolite, mica, apatite, quartz and feldspars.

Today the Oceanview Mine is the only actively working underground mine in this district. The mine is also open to the public for a fee-for-dig, dump screening - which I gleefully attended in April 2016.

Read more: Last Chance to See the Record-Breaking Foxfire Diamond at the Smithsonian

Two things first struck me when I first arrived: firstly, the amazing view from the top of the site, and secondly the beautiful, perfumed smell of wildflowers in the air.

The set up for the mining experience was simple: there was a large dump pile of material which had been taken out of the mine by excavator, around which the screening equipment was situated.

When I first arrived I was allocated a position and screening equipment, and after a safety briefing I was instructed on the most efficient and proficient technique for screening the material. We were given four hours to work the pile; so using a bucket and small shovel I collected a full bucket and returned to my workstation. Two large wooden heavy wire screens allow you to 'sift' the material - the first screen (with the larger mesh) sits atop the second screen with a smaller mesh.

Material collected from the pile is placed in the top mesh, the smaller material of which then passes through to the second mesh. Any larger pieces in the top mesh are then washed and checked for gem-quality material and discarded or kept as required.

The material in the second screen is then washed and checked for gem-quality material. It is thrilling seeing glimmers of colour or good crystal form.

Read more: Getting to Grips with GemTOF Technology

After four hours of happy and productive sifting, it was time to assess the fruits of the day's labours. These included tourmaline (pink, green and black, or 'schorl'), mica, quartz, garnet and beryl. Sadly I had to leave behind some of the larger pieces such as the tourmalines in matrix due to weight restrictions on my baggage, which, whilst not 'gemmy', were still very interesting pieces.

Visitors can also experience a jeep tour of Chief Mountain, which not only offers some breath-taking views but also allows you to catch a glimpse of the active mine entrance and prospects, as well as views of other famous mines in the area. At the edge of the ridge you can see the Tourmaline Queen Mountain, and in the distance you can just about see other former mine workings. 

There is truly nothing better than digging for gem materials - it's a great visit, for both the experience and for the introduction into the techniques in sorting by this method. I thoroughly recommend this to anyone visiting the area - a bonus is the fantastic weather and beautiful countryside whilst there. ■     

This article originally appeared in Gems&Jewellery July/August 2016 / Volume 25 / No. 4 pp. 14-15

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 coloured tourmaline. All photos by Claire Mitchell. 

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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

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

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

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

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

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

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

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 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

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

---

Amethyst has been worn for its lovely purple colour and mystical properties for thousands of years. From the Ancient Romans to the present day, Julia Griffith FGA DGA EG explores how this beautiful variety of quartz has stood the test of time. 

As it is the February birthstone, amethyst has always been linked to love and romance. However, throughout history the gemstone has also been connected to luck, good fortune and general positivity. The anonymous poem below sums it up nicely:

The February-born shall find
Sincerity and peace of mind,
Freedom from passion and from care,
If they, the amethyst will wear.
Let her an amethyst but cherish well,
And strife and care can never her dwell. Anon.       

Understanding Amethyst Gemstones

Amethyst is the purple variety of quartz and out of all of the quartz gemstones ranks at the top for desirability and value. Amethysts are pale pinkish-violet to deep reddish-purple in hue and are most often found as faceted gems, cabochons or carvings. Many rough forms are also used within jewellery including single crystals, clusters or slices of crystal-lined cavities known as geodes.

The most prized amethysts are known as Russian or Siberian amethyst, named after the fine specimens found in these localities. These have a good clarity and rich purple colouration with flashes of red.

Amethyst Dreamscape^TM 53.37 ct cut by John Dyer & CO. Photo by Lydia Dyer

Amethyst Mythology and Meaning 

Historically, amethyst was kept as a talisman as it was believed to counteract the effects of alcohol. The word amethyst derives from the ancient Greek amethustos, which translates plainly to 'not drunk'.  

This mystical belief in amethyst in keeping one sober extends back to 320 BC to the poet Asclepiades of Samos, likely inspired by the wine-like colours of this gem. People believed that wearing an amethyst would save them from inebriation. The more affluent indulgers would sip from carved amethyst goblets or add powdered amethyst into their wine to keep their sobriety.

Amethyst - The Gem of Wine? 

This mystical power was argued as false by Pliny the Elder in the first century AD, however the belief continued for the centuries that followed. Inspired by its association with wine, the French poet Remy Belleau created a myth in the 16th century explaining how amethyst came into existence.

The poem speaks of Bacchus, the Greek god of wine and beautiful maiden named Amethystos, who refused the advances of Bacchus and prayed to the Goddess Diana to keep her chaste. To protect her, Diana transformed Amethystos into white crystal quartz. In frustration, Bacchus poured his wine over the crystals, dyeing them purple forevermore. 

Bentley and Skinner Amethyst Bracelet. Image courtesy of Bentley and Skinner

The belief that amethyst is one of the worlds more precious gems can be linked back to antiquity. Amethyst was one of the twelve gemstones mounted in the Priestly Breastplate, cited in the Book of Exodus. It is from these 12 gemstones that the concept of birthstones developed. Christianity has used amethyst historically within the episcopal rings of bishops and other clergy to represent abstinence from alcohol. 

Amethyst - A Symbol of Royalty

In the Middle Ages, amethyst became a symbol of royalty and the rich purple of amethyst can be found within regal wardrobes and jewels across the world. A large domed amethyst can be found sitting atop the large Imperial Sceptre with Cross in our British Crown Jewels. 

The amethyst was considered a cardinal, or most precious gemstone, and was historically acknowledged in high regard alongside diamonds, rubies, emeralds and sapphires.

Cardinal gems held a value above all others due to their beauty and rarity. An abundant source of amethyst was found in Brazil in the eighteenth century and nowadays amethyst is widely accessible and ready to be enjoyed in all its regal beauty by gem and jewellery lovers worldwide. ■

Read more Gem-A Birthstone Guides here. 

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

Cover Image quartz amethyst rough crystal from the Gem-A archive. 

Claire Mitchell FGA DGA talks to Dr Jeffrey Post, chairman of the Department of Mineral Sciences and curator of the National Gem and Mineral Collection at the Smithsonian Institution, about advanced gem testing, the Hope diamond and the importance of donations to the museum.

Q. Moving forward, how important do you feel advanced testing will be?

I think it's getting there - a lot has changed in the last 10-15 years, particularly when you look at the kinds of sophisticated research instruments that the various gem labs have now. These days you’ve got pretty smart scientists out there trying to figure out ways to treat and enhance stones, so it takes pretty smart scientists and good instrumentation to be able to detect these treatments and enhancements. Nowadays there are labs all around the world that are treating stones - sometimes you don't find out about certain treatments until quite a bit later - so we are in an ‘arms race’ of sorts. It's getting to be fairly sophisticated material science - the kinds of techniques that are being applied are ones that are not always easy to detect, and ones that we would never have imagined that could be done. 

Read more: Getting to Grips with GemTOF Technology

I and many others have made the argument for a long time that we need well-trained scientists working in some of these labs, because the nature and sophistication of what is being done is dealing in the scientific. I think it’s a shame that there isn't a really clear path for someone to pursue research in science that will be directly relevant to gems. 

However, GIA - along with a couple of other groups - have tried to get together some funding to hire post-doctorates to work on gem-related projects, and have provided hands-on training to people that have good backgrounds in chemistry, physics and material science. It's clearly a step in the right direction - in the end you get someone who has that scientific background, but who also has some experience working on gem materials and who has been introduced to the gem world.

I think that the gem industry has some responsibility to try to help fund more of the kinds of research that needs to be done, research which will ultimately benefit the industry. Look at beryllium diffusion treatment, for example. That was something that no one ever expected - who would of thought of diffusing beryllium into corundum to change its colour - it's a pretty sophisticated treatment that took some research to figure out and understand, and then to develop a way to identify it. The trade were actually behind on that process by several years before it was finally cracked. 

It should be thought of as a much longer term investment - thinking about the health of the industry. For the good of all of us we need to figure out ways to be sure that we are staying up to date with technology, research and developments in related scientific fields. 

Q. The Smithsonian carried out advanced testing on the Hope diamond. It was reported that the type of instrumentation that was used created a very tiny hole in the diamond - did it? Was it hard to make the decision to test it in that way?

I hate to say it but it did. The key words here are that the hole was very, very, very tiny - if you look at it under a microscope you still can't see it. However, the decision to test in that way wasn't hard, not once I knew what the technique entailed. We had a pretty good understanding of what we were doing, what the test would involve and how the diamond would respond to it. We have a saying at the Smithsonian, that every specimen in the collection is available for research because ultimately, why are we keeping these things if we are not learning from them?

The Hope diamond is a very rare, blue diamond that is a piece of the earth. We use minerals and crystals to learn something about the earth - the Hope diamond has its own story to tell us about how it was formed, where it came from and how it is different from other diamonds, so I think that the fact that we have it in the collection means that it is available for us to study.

Read more: Harrods Unearths 228.31 ct Diamond from its Vaults for Private Sale

It wasn't just me it was a measured and thoroughly assessed decision. All the way through the tests we kept a close eye on things and made sure that it was working the way we thought it would, and so yes, we knocked a few billion atoms out of there, but no one is going to miss those few billion atoms. 

In the end we learned a fair bit of information about the diamond. We got a lot of publicity after we did that experiment and I think part of the reason for that was that people never thought about the Hope diamond as anything other than a ‘cursed’ gemstone worth a lot of money, so I think for many it was an eye-opener to think of it as something that is worth studying. The fact that it stays in the collection means that we can continue studying it.  

The instrument we use is the Time-of-Flight Secondary Ion Mass Spectrometer (ToF-SIMS) - 10-15 years ago we would never have imagined being able to use such an instrument or for somebody to have one in their department, so who knows, 10-15 years from now what other instrumentation will come along? What other options for testing will we have access to, that are equally non-destructive? It's therefore nice to know that we can go back and continue to try and pull a few little pieces of information from the item and continue to learn its secrets.  

Q. How important is the private sector to the purchase of acquisitions?

It's absolutely critical as the Smithsonian is a public-private partnership. We end up depending very heavily on private donations, particularly endowments that people have set up. Some of these go back 100 years whilst some of them are more recent, so one of our goals is that we are always trying to build up our endowments to continue to support the work that we do. 

Typically the collection has grown not from what we have purchased but from what people have given, so the big private partnerships are the donations that people have given us to help build the collection. Sometimes they come in as a large collection of minerals, sometimes as a single piece of jewellery or a single gemstone. The Smithsonian has been around for a long time (by USA standards, anyway) and so if we continue to accumulate at a steady rate the collection will grow to an even bigger collection. 

Read more: Last Chance to See the Record-Breaking Foxfire Diamond at the Smithsonian

Luckily we have time on our side; we don't need to get everything right away. One of the great parts of my job is the feeling that you are part of something that has had a long history and will have a long future - it's a cool feeling to be a part of something that has longevity associated with it. It gives you context for the work that you are doing and allows you to relax a little bit and say “I don't need to get that thing this year”, or “I don’t need to sell everything to get that one thing”, because that one thing, even if it goes into another collection now, will still be out there. 

It helps me to realise that my job never really had a beginning and doesn't really have an end; you are just stepping in as a caretaker of sorts, you keep things going and hopefully you will do some good things that will result in the collection growing.

As the National Museum of the USA we don’t charge, and so there really is a sense that people feel like the museum belongs to them - there is no better situation than one where you're saying “it's your museum, it's your collection, here's what we would like to do.” ■

The full version of this article originally appeared in Gems&Jewellery July/August 2016 / Volume 25 / No. 4 pp. 28-33

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 Smithsonian's National Museum of Natural History on the National Mall in Washington, D. C. Copyright Smithsonian Institution

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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

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

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

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

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

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

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

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 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

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

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Sarah Steele FGA DGA discusses the many simulants of one of Britain’s most famous native gemstones, Whitby jet.

If imitation is the sincerest form of flattery, then Whitby jet must be a very desirable material indeed. I can think of perhaps 20-30 different materials, both natural and synthetic, which, at one stage or another over the years, have been described as Whitby jet.

We think of a 40-year period during the mid to late nineteenth century as the heyday in Whitby jet manufacture, and from a jewellery output perspective that is unequivocally true. However, the desire for Whitby jet, and the quest to imitate it, has its roots much further back in time. 

Read more: Reconstructed Amber Broken Down

Following the Scottish Gemmological Association’s Conference this year, delegates had the opportunity to visit the 'Celts' exhibition at The National Museum of Scotland. I couldn’t resist the opportunity to join them in having a closer look at the museum’s stunning collection of Bronze Age jet neckpieces whilst we were there.

Historically, many of these early pieces containing black beads with high organic carbon content were described as Whitby jet. Modern analytical techniques have shown, however, that these almost always contain a variety of materials - Whitby jet, certainly - but also oil shales, lignites and cannel coals, often within the one piece of jewellery. 

Whitby jet is a material with which the demand for rough will always outstrip supply in periods of high production, and jet collection requires patience as it is reliant on coastal erosion. Are we then, in the Bronze Age some 4,500 years ago, seeing the first example of a Whitby jet simulant? It has to be noted that the prevalence of Whitby jet in the archaeological record during this period suggests that it is arguably one of the oldest economic resources in the British Isles.

Fast forward 2,670 years and the Whitby jet simulant market is a fascinating and booming industry. British society is participating in a national obsession with mourning. With the death of George IV in 1830, the Lord Chamberlain’s office dictates the dress code for the period, stating unequivocally that “the ornament shall be jet”. In 1830 the term ‘jet’ meant only one material: Whitby jet. The death of the Duke of Wellington in 1852 prompted the production of Whitby jet jewellery into overdrive - the 50 recorded workshops in 1850 swelled to 204 following the death of Prince Albert in 1861, as yet another wave of mourning swept the nation. 

Read more: From Elizabeth I to Elizabeth Taylor with John Benjamin FGA DGA

Demand for rough Whitby jet was beginning to outstrip supply and other options were needed. The main attraction of Whitby jet as a gem material was of course its deep black colour and liquid-like lustre, but more importantly its low specific gravity (SG) 1.2-1.3. It was fine to look ‘weighed down’ by the convictions of your expression of mourning, but it was practical if the seven strings of beads you wore to denote that you were the seventh daughter of a deceased father, didn’t weigh more than a few ounces.

Therefore, to be a convincing simulant of Whitby jet, the imitation material would need to be light in weight. Whitby jet is also a poor thermal conductor and so always feels warm, as heat is not quickly transferred away from the surface. Today we often describe jet as feeling ‘plasticky’, however, in the mid nineteenth century plastic was yet to be discovered. The simulant therefore needed to be light in weight, black in colour and a poor conductor of heat. 

Horn and tortoiseshell

In 1712 John O’Bisset discovered horn could with the application of heat, be moulded into various shapes. When cooled the shape was retained - O’Bisset had discovered the first natural thermoplastic material. Sheets of horn were put between hot metal plates in a press and pressure applied. Placing the warmed horn into moulds before applying pressure enabled the production of horn boxes, beakers and other items. With the application of black dye, pressed horn was a good candidate for a simulant of Whitby jet and many jewellery items were produced. 

Horn has a tendency to delaminate due to its layered structure, so loupe examination often reveals these layers, especially on the reverse of brooches. Any damage to the edges also gives a slight transparency to the damaged area, which is not seen in Whitby jet. The colour can often seem uneven and it is not possible to screw a brooch fitting into jet. Therefore a screw, often seen in horn, is always a sign of a simulant. 

Top: Pressed horn jewellery items. Below: The reverse of a pressed horn brooch showing lamination and screw fittings

It is also worth mentioning that tortoiseshell, like horn, is also a natural thermoplastic. Tortoiseshell, a much admired decorative material, derives not from a land tortoise but from certain species of marine turtle, principally the relatively small hawksbill. Tortoiseshell is unlikely to be mistaken for jet due to the mottled colour, but the SG and ‘plasticky’ feel are similar.

Bog oak

Whitby jet is a fossilised wood, so perhaps a wood product could also make a suitable simulant. Bog oak is not a specific species, rather a term that indicates wood that has been buried in a peat bog for thousands of years. The extremely low oxygen conditions of the bog protect the wood from normal decay. While the underlying peat provides acidic conditions where iron salts and other minerals react with the tannins in the wood, gradually giving it a distinct dark brown to almost black colour. 

Bog oak occurs in many areas of the United Kingdom but jewellery usually originates from Ireland. It was produced from the early 1800s but became popular in the mid nineteenth century, reflecting the demand for Whitby jet, especially after 1852, when techniques to mass-mould and decorate the material (through the application of hydraulic or heated pressure to the dried wood) were invented. 

Although predominantly used for mourning jewellery as a cheap substitute for Whitby jet, bog oak was also worn to support Irish crafts, with pieces often carved or stamped with Gaelic motifs such as harps or shamrocks - symbols not normally found in mourning jewellery. Concentric rings are usually visible on the reverse of items as blanks were lathe-turned prior to carving. Loupe examination always show the ligneous nature of the wood and the lustre achieved is usually textured and dull.

Vulcanite

In 1839 Charles Goodyear discovered the method of mixing sulphur with rubber to form hardened or vulcanised rubber, called Vulcanite. The proportion of sulphur can be increased or decreased in order to vary the required amount of hardening accordingly. Between 25-50% sulphur gives a hard product with the familiar feel of plastic. There are many Victorian vulcanite objects, but the most common form is an imitation of Whitby jet used widely in the production of brooches, bracelets and necklaces. Vulcanite could be produced in almost any colour, although the predominant colours are black (ebonite) and brown. As a result, vulcanite was by far the most widely-produced Whitby jet simulant. Unlike pressed horn a thermoplastic materials which, if heated again can be re-moulded into a different shape. Vulcanite is a thermoset material which, after moulding becomes brittle and cannot be remoulded. 

Vulcanite can be distinguished from jet relatively easily. If the material has been exposed to light over time it loses its black colour and becomes khaki brown. When rubbed, vulcanite smells strongly of sulphur and brooch pins are usually screwed into position rather than glued. Chain links only show one or two splits depending on the link style as the link can be twisted open and then closed. In comparison in Whitby jet links, where every other link in the chain is cut and glued and will always show two or three cuts depending on the style of link. As vulcanite pieces were often moulded from jet originals the same design is seen regularly and, with experience, can be identified easily. (Please note: the ‘streak’ test on vulcanite will reveal a light brown streak similar to that of hard Whitby jet and so should not be relied on).

Bois durci

In 1855 Francois Charles Le Page secured a French patent for a method of combining blood albumen from slaughterhouses, with wood powder to form a plastic mouldable material he called bois durci. The wood dust (either ebony or rose wood), was mixed with blood, dried and then ground to a fine powder. The powder was placed in a steel mould and steam heated to 150-250°C in a powerful hydraulic press. After half an hour the mould was plunged into cold water. The resulting wood product was an extremely dense, highly polished and resistant thermoset material. 

Le Page is reported to have used the marketing strapline “Anything Whitby Jet could do, bois durci could do cheaper and in brown”. The most common items available in bois durci today are circular plaques showing royalty or statesmen of the time. They are generally brown and often have bois durci stamped on the reverse.

French jet and Vauxhall glass

As far as Whitby jet imitations go French jet, along with vulcanite one of the most common. Glass items were also produced in large quantities during the Whitby jet heyday, primarily faceted black glass beads referred to as French jet. 

Its higher SG, vitreous lustre and glass moulding marks mean it is unlikely to confuse French jet with Whitby jet. However, because many of the designs were so innocuous, finding a nineteenth century piece of French jet and identifying it from a piece of black glass, used all the way through to the 1940s, can be difficult for collectors of the material. 

Vauxhall glass is often referred to as the English version of French jet, however all French jet was not of course produced in France! This thin highly reflective mirror glass was produced by a silvering process. The silvering is often seen on the reverse - either intact or in residual traces.

Spanish jet

Although all the above impacted the Whitby jet industry, it was a natural jet which was finally responsible for the industry decline. By 1870 the Whitby jet industry reached its peak, before catastrophically collapsing. There were undoubtedly a number of reasons. Some blamed the terrific demand, which had outstripped supply and lead to a fall in standards of workmanship, as many workers hadn’t had the basic training. The large number of simulants also cannot have helped, but the final death knell was heralded by the arrival from the continent of Spanish jet. It is hard to estimate how much of this material was imported from Asturias, but it is first documented in 1874 and many tonnes seem to have been available. 

The Spanish jet trade had flourished between seventh and sixteenth centuries, and whilst the Spanish supply undoubtedly had some very good quality rough material, it seems that Whitby imported a rather poor quality jet, often containing pyrite, making it unstable. Finished pieces degraded quickly, cracked and crumbled. As a result, consumer confidence in an already struggling product sector collapsed.

Decline of the industry

In 1889 the Whitby Gazette reported “It would have been better for the Whitby jet Industry, and better for art development, if the Spanish jet trade had never been known in Whitby”. Despite desperate measures to support the Whitby jet industry, such as a quality mark scheme, the industry didn’t recover. The mourning trend was well and truly over. 

In 1915 The Lady described the Whitby jet trade as “A somewhat funereal fetish of fickle fashion”. Poor recognition for the greatest lapidary trend our nation, and perhaps the world has ever seen. 

The beginning of the twentieth century may have heralded the end of the Whitby jet mourning jewellery trend, but it didn’t signal the end of the road for the use of plastics in jewellery. In 1899 we saw the introduction of casein formaldehye; milk curds hardened with formaldehyde giving us such famous trade names as Galilith, and of course in 1907 phenol formaldehye, with wood flour or other filler as powder gives us the trade name Bakerlite. Galilith and Bakerlite were never used to imitate Whitby jet jewellery - by this time (and forgive the pun) you wouldn’t have been seen dead in this outdated material.

It seemed like the end of the road for Whitby jet. The last apprenticed jet worker Joe Lyth died in 1958, and with him died the secrets of the Victorian era. However, the last 30 years or so we have seen a revival in fortunes within the Whitby jet trade. Today there are 11 manufacturers in Whitby town. As mentioned previously, demand for rough Whitby jet is high and patience is required for collection of beach material. This has allowed poor quality materials, primarily Siberian cannel coals and Georgian jet (both often referred to as Gagate) with its poor stability and high porosity to enter the supply chain. 

Georgian jet is becoming increasingly common as finished contemporary style jewellery made by Baltic amber manufacturers, and within the last 12 months as antique style beads from an undisclosed source. Attempts were even made to sell rough to unsuspecting workshops in Whitby. Experienced lapidaries however quickly identified the new foreign imposter. In Whitby we have no issue with Georgian manufactures producing items from their indigenous jet, but lack of disclosure of origin leads to the material being retailed as Whitby jet somewhere along the pipeline.

Nomenclature and appellation of origin is, as always, crucial to price. A good Whitby jet string of Victorian beads is worth £300 upwards, the Georgian imitation probably nearer £20, so caveat emptor!

As a lapidary in Whitby, I know that the Whitby jet trade will, as always fight back against the latest simulants. A true jet to rival the beauty or stability of Whitby jet has yet to be discovered, but it does make me proud to think that for the last 4,500 years Whitby jet has been held with such reverence that many have tried to emulate it. With the desire of the Victorians to find the perfect simulant, Whitby jet was in part perhaps responsible for the birth of the modern plastics industry, and therefore the modern world as we know it. ■

This article originally appeared in Gems&Jewellery May/June 2016 / Volume 25 / No. 3 pp. 16-20

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 fine Whitby jet cameos including King Oswy and his bride (centre) and Bejamin Disraeli (right). Photo Credits Sarah Steele, except where otherwise stated. 

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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

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

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

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

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

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

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

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 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

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

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Jack Ogden FGA looks into the story of the world's second largest blue diamond, the Mouawad Blue Diamond, previously known as the Tereschenko Blue Diamond. 

In the summer of 1984 David Warren, now Senior International Jewellery Director at Christie’s, received a phone call from the auction house’s bank manager with a question: “Do Christie’s sell blue diamonds? Our client has one the size of a pigeon’s egg.”

Mouawad-Tereschenko Blue Diamond

The huge gem turned out to be the Tereschenko diamond, one of the least well known large blue diamonds, and at 42.92 ct, just a shade smaller than the 45.52 ct Hope. It sold at Christie’s in Geneva in November 1984 for a then-record price of $4.6 million to Robert Mouawad and is now called the Mouawad Blue. Unlike the Hope and many of the other famous diamonds, it has lacked a romantic history.

There has been no curse or celebrated Mughal emperor to add notoriety or spice. The Christie’s catalogue, and Lord Balfour in his standard work on the world’s great diamonds, simply notes that the first known appearance of the stone was in 1913 when the Ukrainian Mikhail Tereschenko left it with Cartier in Paris. 

Read more: Harrods Unearths 228.31 ct Diamond from its Vaults for Private Sale

In 1915 he instructed them to mount it in a necklace, which was returned to him in Russia before being spirited out of the country again in 1916, on the eve of the Russian Revolution. Then according to Christie’s and Balfour, it passed into anonymous private ownership until it came up at auction in 1984. 

Perhaps we can now add some spice, even a curse, to this story, by introducing a French dancer born in the final decade or so of the nineteenth century. She entered the entertainment world under the stage name of Mademoiselle Primrose and by 1911 was performing in Le Théâtre des Capucines in Paris. She was renowned for her attractiveness and, in a rather surreal article on the components of female beauty in Paris that appeared in various American newspapers in late 1911 and early 1912, she was noted as one of the most beautiful of reigning stage beauties in Paris with particular praise for her “most charming chin”.

If Mikhail Tereschenko left the 42.92 ct blue diamond with Cartier in Paris in 1913 he may have encountered Mlle Primrose in that city. This is not such a wild suggestion because in 1924 we hear of a former Parisian dancer named Mlle Primrose, real name Suzanne Marie Blanche Thuillier, who had resided for a time in St. Petersburg, Russia, and who moved in Court circles there. She had left Russia for France just before the Revolution and was the owner of what was described as a 43 ct blue diamond, called by some the ‘Russian Imperial Blue’, and by others (rather bizarrely) the ‘Blue Diamond of Ceylon’.

The newspapers at the time gave myriad origins for the stone, neither verified nor mutually exclusive. It came from the eye of an idol in India; reached Russia in the time of Peter the Great; had been set in the Russian Crown Jewels; had been secretly purchased in London “under romantic circumstances” and so on. 

One newspaper even hedged its religious bets and said the gem had “ornamented the finger of Buddha in a Hindu Temple". Particularly intriguing is a report in a British newspaper that "In April 1912, there were rumours in Hatton Garden that a diamond merchant was walking about with a quarter of a million in his wallet. In fact he had received from his Dutch agents a stone [a large blue diamond] which had been sent from America with instructions to let it fetch what it would."

This merchant supposedly pieced together the history of gem, found out that it had once belonged to the Russian Imperial family and put out feelers, which reached the then-Czar who sent an emissary to obtain it. Perhaps more about this supposed transaction will come to light, but in the meantime we can observe that a presence on the market in London in 1912 would tie in nicely with Tereschenko depositing a large blue diamond with Cartier in Paris in 1913.

After Mlle Thuillier and her diamond reappeared in France, some newspapers reported that she had been given it by Czar Nicholas as a token of his regard for her; others that it was given to her by "a member of the Imperial Court of Nicholas".

The latter view was supported by those in the know who vehemently denied, or expressed indignation, at the suggestion that the late Czar gave Thuillier the diamond. Indeed, according to Le Parisien newspaper in June 1924, when directly asked where it came from Thuillier explained “evasively” that strictly speaking she was not admitted to the imperial court, but “frequented assiduously with the gentlemen of the court who occupied the highest positions”. She never claimed that the diamond was presented to her by the Czar. So, if a gentleman other than the Czar gave her the gem, Mikhail Tereschenko is perhaps a potential contender. 

Was a gift of the blue diamond the ticket to a new life outside Russia on the eve of the Revolution? She reportedly arrived in Nice in the South of France in 1916 and pawned it there that same year. The diamond had travelled in a secret pocket of her sealskin coat. 

Following her arrival in the South of France, Mlle Thuillier’s beauty and attire "made her a spectacle among the many lovely women". However, she gambled excessively and this "most notoriously extravagant woman in Europe" inevitably got into debt and had to pawn the blue diamond more than once. In June 1924 the diamond was in pawn for 200,000 francs with creditors circling, but there was the expectation that it would be redeemed and available for purchase. Apparently a Parisian dealer had already offered £125,000 and an American woman £200,000. 

What then occurred is unclear. There are reports that a Joseph Paillaud of Cap d’Ail, near Nice, had put up collateral of 1,350,000 francs and would take ownership of the diamond if not repaid in full by 9 December 1924. Mlle Thuillier made a plea to the Court and in March 1925 the Civil Court in Nice removed it from Paillaud’s possession.

Apparently Paillaud’s actions equated with acting as a pawnbroker, an activity for which he was not licensed. A police search of his house - named, ironically, Chalet Russe (Russian Chalet) - revealed numerous pieces of jewellery lacking the required hallmarks plus records of transactions that were not properly registered.

Mlle Thuillier might well have predicted Paillaud’s bad luck. A newspaper report in 1929 recounted that she had believed the diamond to be cursed. This may be typical press sensationalism, but some accounts say she was something of a mystic with an interest in the occult and in 1924 was even considering taking the gem back to India so it might be replaced on the statue of Buddha from which it had been robbed. It clearly never made it back to the statue and the last we hear of the large blue diamond is in March 1925, in the custody of the clerk of the civil court in Nice.

The last we hear of the celebrated Mlle Primrose - with her charming chin - is in jail in Nice in April 1929, after several years of dire poverty. Her desperate situation had driven her to forgery. What happened to the large blue diamond from 1925, until it resurfaced at Christie’s Geneva in 1984 is so far unknown, but a French newspaper in 1924 had already commented that the diamond had "undoubtedly not yet finished the cycle of events of its adventurous life". 

Note: The above was compiled from contemporary press accounts from Europe and America. Their lack of accuracy is demonstrated by their confusions and contradictions, so for now this is a tale of the Mouawad-Tereschenko diamond, not necessarily the tale of the Mouawad-Tereschenko diamond ■

This article originally appeared in Gems&Jewellery March/April 2016 / Volume 25 / No. 2 pp. 32-33

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 an exact CZ replica of the Mouawad blue.

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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

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

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

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

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

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

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

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 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

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

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Gem-A member Patricia Campion reports on a recent gemmological field trip to Myanmar, highlighting her experiences of gemstone market places, the Myanmar Gems Museum, in Yangon, and seeing mushroom tourmaline for the first time.

On Christmas Day, our group met in Yangon for a gemmological tour of Myanmar organised by Pauline Jamieson for the Scottish Gemmological Association. Just before we left for Myanmar, our plans suffered a fundamental blow with the Government closure of Mogok to all foreigners due to local civil unrest. However, the organisers did a wonderful last minute job of rearranging our itinerary to ensure that we saw and did much to make up for missing out on the famed ruby mines.  

Read more: Gem Central With Gem Dealer Marcus McCallum

Our gem tour proper commenced in Myitkyina (pronounced My-chee-na), which is home to Myanmar's licensed amber markets. Much of the local amber is a distinctive deep red, although a wide spectrum of colour was available. Burmese amber deposits are considerably older than Baltic amber (up to 100 million years old) and the quality and clarity was high, with some very fine specimens containing preserved insects and plants. The market sold a wide variety of jewellery, carvings and beads as well as rough amber.

As is true all over Myanmar, traders were friendly and very pleasant but prices were higher than expected due to the proximity of the Chinese market.

We also visited some interesting local emporia specialising in jade and got our first glimpse at the many and varied hues available, from magnificent, almost translucent imperial jade through the spectrum of greens, greys and lilacs to white jade and almost transparent 'ice' jade.  

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

Arriving in Mandalay, we sallied forth into the infamous Mandalay jade market. Moving at speed through the crowded, cramped space where experts trade jade, we were surrounded by frenetic activity making it an unreal but truly exhilarating experience. In the lower octane atmosphere of the surrounding stalls outside the official jade market, pieces of rough jade could be purchased inexpensively.

Next we visited a family run business selling good quality Mogok ruby at reasonable prices. Their stones had received some heat treatment, but were lively and of good colour and devoid of fissure filling or other undesirable treatments. Later we met gem dealers who had travelled from Mogok, offering a large stock of mainly spinel, peridot, ruby and sapphire.

Star ruby and star sapphire were plentiful, with sapphire tones ranging from deep blue through purples and pinks to silvery grey and creamy yellow. While some stones were marred by rather crude cutting or damaged through poor storage (endemic across Myanmar it seems), the variety of colours available in spinel in particular, was superb.   

Read more: Getting to Grips with GemTOF Technology

The Myanmar Gems Museum, in Yangon, afforded us a wonderful overview of the many rich treasures of Myanmar. Emporia housed within the same building yielded deep green peridot and pale but very clean aquamarine as well as the usual spinel, ruby and sapphire. Many of us appreciated the colour zoned or bi-coloured unheated sapphires, considerably paler than the famed Burmese blue, but prices were prohibitive.

Colourful zircons and sizable rutilated topazes were also plentiful. However, the highlight was the discovery of mushroom tourmaline - a remarkable phenomenon which occurs near Mogok. The ones we saw were grey to pale pink in colour and we also managed to unearth wonderfully colourful cross section slices.

Our time in Yangon encompassed visits to the famed Mogok Street, where many gems are traded, and a whistle stop tour of Bogyoke Aung San Market (formerly known as Scott's Market) where we got our first real chance to see Myanmar golden pearls among other treasures. We also got the opportunity to trade ourselves and perching on stools on a street corner we were instantly surrounded by dealers. Their stock was again mainly ruby, spinel and sapphire both rough and polished, plus some wonderful but rather pricey zircons.  

The expertise and insight of our guide, Duncan Baker, meant that we got an unparalleled glimpse into Myanmar's phenomenal world of gems during our trip. As we departed back home we all agreed that if Mogok reopens we will return to this lovely country with its fabulous treasures and wonderful people. ■

Adapted by the author from an article originally written for the Scottish Gemmological Association. 

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 rough amber samples. Image courtesy of P. Jamieson

---

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

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

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

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

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

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

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

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 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

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

---

This article by Guy Lalous ACAM EG summarises a study of the geology, gemmological and physical properties of rubies and pink sapphires from Aappaluttoq, one of the last pristine spots on the planet not far from the arctic circle. 

What is the difference between metamorphism and metasomatism?

When rocks change because of an increase in the pressure and/or temperature of their surroundings, it is called metamorphism. When metamorphism is accompanied by a change in the chemistry of a rock, the rock is said to have been metasomatised. Metasomatism involves changes in mineralogy and structure along with the addition and/or removal of elemental constituents.

What are mafic and ultra-mafic rocks?

Both are igneous rocks. In essence, igneous rocks are formed through the cooling and solidification of magma. Ultramafic rocks are igneous rocks with low silica and gas contents which makes them very fluid. Ultramafic rocks are given names depending on whether they are intrusive or extrusive. Peridotite is the name given to intrusive ultramafic rocks, komatiite is the name given to extrusive ultramafic rocks.

Mafic rocks are mostly composed of pyroxene, calcium-rich plagioclase, and minor amounts of olivine. The mafic magmas are somewhat more viscous than the ultramafic magmas, but they are still fairly fluid. Additionally, they contain somewhat more gas than the ultramafic magmas. Gabbro is the name given to intrusive mafic rocks, whereas basalt is the name given to extrusive mafic rocks.

The corundum from Greenland occurs within a phlogopite-bearing metasomatic rock. The rocks at Aappaluttoq have been subjected to high-pressure, high-temperature metamorphism. The mineralisation at Aappaluttoq is hosted by a reaction zone that formed from metasomatic interactions between ultramafic rock (peridotite) and mafic rock (leucogabbro). The peridotite has low silicon oxide (45 wt.%) and contains various chromophore elements (particularly Chromium, but and also vanadium, iron and titanium). The leucagabbro has an aluminium-rich composition.

During regionals metamorphism, fluid interactions between the two differing rock types created a metasomatic reaction zone encompassing part of the peridotite, the leucogabbro and the contact zone between the two units. Upon regional cooling, the reaction zone formed significant volumes of stable phlogopite with corundum. The availability of chromium from the peridotite allowed the substitution of Cr³⁺ for Al³⁺ in the corundum, producing its pink to red colour.  

Read more: Exploring the wonders of Myanmar

Standard gemmological properties are consistent with metamorphic-metasomatic-type rubies and pink sapphires from other world deposits. Typical inclusion features consist of coarse particles and fine needles of rutile, as well as inclusions of mica, talc, pargasite, cordierite, sillimanite, plagioclase and boehmite. Healed fissures and twinning complete the story. Catapleiite, chlorite, cosalite, dolomite, magnesite, margarite, pyroxene and sapphirine were reported in a previous study.  

A translucent, whitish inclusion of talc commonly observed in rubies and pink sapphires from Greenland. Magnification x58. Image courtesy of C. P. Smith

Spectroscopy in the visible range yielded following data: weak-to-distinct lines were observed at 468 nm and at 475/476 nm along with faint lines at 659 and 668 nm, plus two strong lines at 692 and 694 nm (which appeared as a bright emission line at 693 nm).  

Read more: Reconstructed Amber Broken Down

In the mid-infrared region of the spectrum, some rubies and pink sapphires from Greenland showed distinct bands at approximately 3310 and 3075 cm⁻¹ (and weak bands at approximately 2100 and 1980 cm⁻¹). These features indicate the presence of boehmite, which was mostly concentrated along intersection tubules related to twinning and/or parting planes. Such absorption characteristics are helpful not only for identifying the presence of foreign mineral phases, but also for proving that a gem has not been heated. 

What about origin determination and treatments?

A genuine untreated ruby is increasingly rare and non-treated gems fetch a substantial premium. Proven origins such as Kashmir for sapphires or Mogok for rubies may considerably contribute to the value of a gemstone. The trade is therefore requesting origin determination from gemmological laboratories. It all started with a microscopic approach in the eighties and developed over time as chemical and spectroscopic criteria were introduced.

Crystal growth characteristics, inclusion identification using a Raman microprobe and analytical tools such as Laser Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) have been incorporated into the routine of gemstone analysis.

Consequently, access to chemical elements is gained at very low detection limits. The latest technological development Inductively Coupled Plasma Time-of-Flight Mass Spectrometry (ICP-MS-TOF) allows trace-element characterisation of gemstones for origin determination and treatment detection, is fit for age dating, inclusion studies and high-spatial-resolution chemical mapping of gems.  

Read more: Getting to Grips with GemTof Technology

The chemical composition of the Greenland rubies and pink sapphires is characterised by relatively high iron contents and comparatively low concentrations of titanium, vanadium and gallium. The iron content separates them from the majority of stones from marble-type deposits.

Rubies and pink sapphires from basalt-related deposits also contain relatively high iron, although correlations between other trace elements can help to separate them from those of Greenland. The iron content of our Greenland stones was similar to that of some rubies and pink sapphires from East Africa. Further work on the trace-element and isotopic composition of the Greenlandic material is ongoing and should prove helpful for origin fingerprinting. Certain mineral inclusions such as cordierite, cosalite and catapleiite may point to a Greenland origin.  

Modern mining techniques are planned to maximise production and minimise cost. The mine economics were modelled using only melee-sized rough gem material. Pink sapphire makes up approximately 60-80% of the production, with ruby making up the balance. None of the stones included in the study were heat treated. It should be expected that heated Greenland corundum will become available at some point. The deposit has the potential to make an important contribution to the global supply of ruby and pink sapphire for many years. ■

This is a summary of an article that originally appeared in The Journal of Gemmology entitled ‘Ruby and Pink Sapphire from Aappaluttoq, Greenland’ Christopher P. Smith, Andrew J. Fagan and Bryan Clark 2016/Volume 35/ No. 4 pp. 294-306

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 partially healed fissures composed of groups of isolated negative crystals. Magnification x55. Image courtesy of C. P. Smith

---

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

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

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

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

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

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

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

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 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

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

---

Those born in March are lucky enough to have two birthstones: the beautiful blue of aquamarine and the mysterious red-spotted bloodstone. Here, we delve into the history and mystical properties of aquamarine and why this sky blue gem is said to be a talisman of good luck, fearlessness and protection. 

The blue hues common to this popular stone are fitting considering the Latin translation of aquamarine is 'water of the sea'. Legends describe it as the mermaid's stone, bringing luck to sailors and protecting them from the perils of ocean travel.

In crystal healing, aquamarine is thought to have soothing energy that quells phobias or irrational fears. It is also associated with the throat chakra and is said to help boost the confidence of public speakers.

From a gemmological perspective, aquamarine is a member of the beryl family of gemstones, which also includes emerald, heliodor, morganite and goshenite. Aquamarine is distinguished from these gemstones by its pale blue to bright blue colour, caused by iron in its chemical composition.

Many aquamarines available on the market have been heat treated to enhance their colour. A yellowish, greenish or bluish-green beryl can be heat treated to produce a stable blue colour or irradiated to produce the yellow of heliodor.

Read more: Exploring the wonders of Myanmar 

Aquamarine displays pleochroism, which means its presents multiple shades of colour at once. Untreated aquamarine can be pale blue, bright blue, green and colourless. It has a hardness of 7.5 on the Mohs scale. 

Where is Aquamarine Found?

Aquamarine is mainly found in Africa and Brazil, however, the March birthstone can also be mined in Australia, China, Myanmar, Pakistan, Madagascar, Russia, USA and Sri Lanka. In the 1950s, a famous and historically-significant deposit of aquamarine was found in Minas Gerais, Brazil, and the gemstones recovered became known as Santa Maria Aquamarines. Many gemstones from this location are highly-prized for their unusually deep blue tone. Today, you may come across the term 'Santa Maria' used to describe a particularly lovely blue colour aquamarine. 

Distinguishing Features of Aquamarine 

Aquamarine often occurs as hexagonal-shaped long prismatic crystals, with striations and rectangular etch marks occasionally found on the prism surfaces. 

Aquamarine's durability and plentiful supply makes it a popular choice among jewellery designers. It can also be fashioned into most cuts, making it a firm favourite with lapidaries. 

Read more: Meet Renowned Gem Cutter John Dyer

Although many cut aquamarines are free of inclusions, two-phase inclusions (liquid and gas filled), spiky cavities, and tubes parallel to the length of the crystal that look like falling rain are common.

The Dom Pedro Aquamarine

Perhaps the most famous aquamarine specimen is the 10,363 ct Dom Pedro, which weighs an astonishing 26 kg. To this day, it holds the title of being the largest piece of aquamarine ever to be cut. It was specialists in Idar-Oberstein, Germany, who took on the challenge in 1992.

Discovered by three Brazilian miners in Pedra Azul, Minas Gerais in Brazil in the late 1980s, the original aquamarine was a metre-long. Accidentally dropped, the specimen fractured into three separate pieces - the Dom Pedro being the largest. 

In 1991, Jürgen Henn from Idar-Oberstein visited the owner of this large aquamarine crystal. In 1992 the stone went on the market and Jürgen asked his colleague Bernd Munsteiner to assess at the stone. Bernd sent his son, Tom Munsteiner and Jürgen’s son, Axel Henn, to strike a deal in Brazil and bring the stone to Germany. 

For a year Bernd worked on the stone, studying the crystal, drawing facet patterns, cutting, faceting and polishing, before transforming the rough stone into an incredible obelisk.

The Dom Pedro first went on public display in 1993 in Basel, Switzerland. Some years later, it was destined to be cut into many smaller stones, but it was rescued by Jane Mitchell, who generously donated the Dom Pedro to the Smithsonian National Museum of History in Washington DC, USA. 

Read more: An Interview with Dr Jeffrey Post of the Smithsonian Institution

This awe-inspiring gemstone is in the permanent collection of the museum, housed in the National Gem Collection Gallery. ■

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 beryl aquamarine crystal. Photo credit Pat Daly. 

---

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

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

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

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

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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

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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

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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

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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

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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

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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

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Tom Dodge, a retired geologist living in Arizona, USA has been an avid rock collector for 57 years, a registered professional consulting exploration geologist for 35 years, a skilled flint knapper for 16 years and a budding lapidary for two years.

Here, he takes a look at fire obsidian, an enchanting and little-known material. Collecting and working fire obsidian has truly become his passion and he blames (and sincerely thanks) Emory Coons, the master of this spectacular material for being a generous tutor.

Fire Obsidian

Fire obsidian, a particular variety of iridescent obsidian found in the northwest USA, displays various brilliant colours and patterns. When carefully worked by the lapidary, exquisite gems can be produced that in the author’s opinion, are equal to the finest examples of other iridescent gems in ‘play of colour’, brilliance, uniqueness and intrinsic beauty. To date this location is the only occurrence of fire obsidian known. 

History of Iridescent Gems

Iridescent gems and minerals have held a special fascination for man throughout history. Many early attempts were made to describe both the cause of the iridescence and the metaphysical properties believed to be associated with them. 

Read more: What are the different types of opal?

In ancient times precious opal was considered a stone of great benefit to the eyes and was worn to cure ocular ailments, as well as to render the carrier of the stone invisible to the eyes of others (Braid, 2015). Fire opal was admired as a symbol of fervent love in ancient times among the peoples of India, Persia, Central America and North America.

Read more: How to asses the value of an opal

It was believed that a gem that bubbled over with vivacity to such an extent as the fire opal could have been created only in the waters of paradise (International Coloured Gemstone Association, 2015). The Mayans and Aztecs particularly loved this gemstone and used it in mosaics and for ritualistic purposes. Today rainbow obsidian is believed by some to be particularly powerful in meditation to dissolve shock, fear or barriers. 

Optical Effects in Gemstones

Optical phenomena are caused by the light-dependent properties of a gem. They are not due to its basic chemical and crystalline structure, rather the interaction of light with certain inclusions or structural features within the gem. Iridescence is the phenomenon seen as a multi-coloured surface effect caused by diffraction. As white light passes through very small openings such as pores or slits it is diffracted and a prism effect causes it to separate into spectral colours. This diffraction creates the rainbow display of fractures, the colours of labradorite, and the ‘play of colour’ of precious opal. 

When colour waves reflect through thin layers of material, which differ in refractive index, a loss of some colours and a reinforcement of others can take place. This gives rise to dramatic colour blocks, which may shift with viewing angle. 

What Causes the 'Fire' in Fire Obsidian?

Recent laboratory analysis has determined that the ‘fire’ in fire obsidian is caused by thin-film interference. Examples of this form of interference include the sheen of soap bubbles on a sunny day, the streaks of colour on a freshly wiped windshield, and a colourful film of oil on a rain puddle - these are all the results of the interference of light by a very thin film of one material that is spread over the surface of another material. 

Collected samples of fire obsidian were investigated with field-emission scanning electron microscopy, X-ray energy-dispersive spectroscopy, electron back-scatter diffraction and optical spectroscopy methods (Ma et al., 2007). The study revealed that thin layers (flow bands) within the obsidian have a thickness of 300 to 700 nm and are enriched with nano-metricised crystals of magnetite. The colour is caused by thin-film optical interference, in which the thin iron-enriched layers have a higher calculated index of refraction (1.496 < n 1.519) than that of the host glass (n = 1.481). 

Iridescence is the most widespread of the optical phenomena and can be observed in pearls, fire agate, ‘rainbow calcite’, some obsidians and iris agate. When iridescence is combined with interference, thin-film interference occurs (The Physics Classroom, 2015). 

Formation of Obsidian

Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure. The result is volcanic glass with a smooth uniform texture that breaks with a conchoidal fracture. It is an amorphous material known as a ‘mineraloid’. Pure obsidian is usually dark in appearance, although the colour varies depending on the presence of impurities. 

Read more: Exploring the Wonders of Myanmar

Iron and magnesium typically give obsidian a dark green to brown to black colour. Very few samples are nearly colourless. Certain types, however, display iridescent patterns due to dense and relatively homogenous concentrations of minute suspended inclusions of magnetite that act like diffraction gratings. Descriptive trade names like ‘velvet’ or ‘rainbow’ obsidian are used to market these varieties. 

The volcanic highland hosting the fire obsidian is located in southeast Oregon and is an extinct rhyolite dome complex that encompasses approximately 90 km2 at altitudes of 1,400 to 1,950 m (Walker and MacLeod, 1991). Most of the volcanic deposits, which include numerous varieties of obsidian, rhyolite flows and dykes and perlite have been dated at 4-5 million years old on the basis of potassium- argon age dating (Walker et al., 1974). Post-eruption weathering and erosion have removed much of the youngest volcanic deposits, locally exposing older sections of the rhyolite dome. 

Although extensive deposits of a wide variety of obsidian occur in the area, fire obsidian has been found only in small localised dykes, which appear to be intimately related to, and sub-parallel to, rhyolite dykes. Zones containing the bright colour bands exist as small, isolated and discontinuous ‘pods’ within weak to strongly flow banded black or brown obsidian. 

These flow bands are generally aligned sub-parallel to the orientation of the obsidian dykes (Miller, 2006). Hard labour is necessary to excavate the fractured but compact material. Approximately 10 to 20% of the total volume extracted will have the potential to contain fire layers and only about 5% of that amount will contain fire. Fresh from the ground, the irregularly shaped and sized pieces are dirty and opaque. Small test chips can be carefully removed to inspect for the faint thin flow bands. More detailed inspection may reveal the sought-after bright fire reflecting from the band(s). Then the work begins. 

Fire obsidian is excellent for cutting and polishing into unique and spectacular cabochons. First, the stone must be cleaned, and then a detailed ‘reading’ of the rock (to determine the exact location and orientation of fire layers) is performed. This is a challenging procedure as every piece is unique. 

Some layers reflect many colours in bands and patterns, with sharp boundaries between the colours, while in other stones the colours may overlap each other. Colour may exist only on part of the layer, leaving the remainder of the same layer a dull grey. 

Fire Obsidian Colours

The colours and intensity of the iridescence (the ‘flash’) can be highly variable along the same layer. Some layers reflect colours on both sides, while others reflect colours on only one side. The colour can occur as single isolated layers in the stone or as several colour layers stacked very closely on top of one another. 

Reflective layers are rarely flat. They often undulate and change orientation, usually to a small degree, but these shifts can be abrupt and drastic. Some layers are so contorted as to turn and double back on themselves. The colours reflected by a single layer can have colours that range through the entire spectrum, while other layers display a single colour. Additionally, patterns (striations, blotches, ropes, wrinkles, straw-like shoots, rods and others) observed along with the reflectance can be highly variable. 

The cause of these patterns is not known but is possibly the result of small localised differences in the thickness or the orientation of the magnetite enrichment along the flow bands. Successful cutting and polishing of fire obsidian is extremely challenging for the lapidary. Diamond cabochon-making lapidary equipment is ideal for working this material. 

Locating and isolating nano-metric layers within black glass requires skill, diligence and a great deal of patience. Obtaining a high ‘wet’ polish on black glass is difficult and time consuming. Ideal results are achieved using expensive polishing agents such as optical grade cerium oxide.Equipment contamination is a strong concern at all stages of grinding, sanding and polishing, and must be avoided.

Collecting Fire Obsidian

Fire obsidian is relatively new to the gem and jewellery community and is known to occur at only one location worldwide. The collecting of fire obsidian is labour intensive and successfully working the material by the lapidary is challenging, expensive, time consuming and tedious. Recent initial marketing efforts have resulted in high interest from jewellers and collectors in finished cabochons and polished windowed specimens. While rough material is seldom available, proven pieces in the form of small slabs or unpolished ‘windowed’ stones are available to the lapidary.

For more information about this material contact Tom at tdodge101@gmail.com. ■ 

This article originally appeared in Gems&Jewellery Jan/Feb 2016 / Volume 25 / No. 1 pp. 19-21

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 an example of the beautiful colours found in fire obsidian. All images show samples created by and belonging to either Tom Dodge or Emory Coons. Photo Credits Jeff Scovil.

Sarah Steele FGA DGA discusses the unusual history of ancient Preseli bluestone. 

If ever there was an unlikely candidate for a gem material then Preseli spotted dolerite, would at least at face value, be it. Over the last five or six years however it has appeared on the market in increasing quantities, both as jewellery and ornamental items, prompting English Heritage and the National Trust to consider unprecedented measures in order to restrict its sale, leading to an ethical debate: should this native material, which has been important to the occupants of the British Isles since 2900 BC, be available for our general consumption or removed from the market to protect the suggested source of the raw material? 

It seems that the people of the twenty-first century have a desire to own a piece of the material, which has almost come to represent the Stone Age, a material of such importance to our Neolithic ancestors that they engaged in a seemingly impossible feat of human engineering, moving huge blocks of this material 250 miles in order to build one of the world’s most iconic ancient monuments - Stonehenge. 

Stonehenge

Stonehenge, on Salisbury Plain, Wiltshire has been a designated a UNESCO World Heritage Site since 1986, ranking alongside sites such as Machu Picchu in Peru and the Xian Terracotta Warriors in China. 

It is a complex site, best known for the standing stones - the collective landscape of which, in association with other surrounding structures, demonstrates Neolithic and Bronze Age ceremonial and mortuary practices resulting from around 2,000 years of continuous use between 3700-1600 BC. The sheer size of its megaliths, the sophistication of its concentric plan and architectural design, the shaping of the stones and the precision with which it was built, secures Stonehenge as one of the most impressive prehistoric megalithic monuments in the world. 

The large stones that form the Outer Circle are known as ‘sarsens’. They are hard, resistant sandstones thought to have been collected from glacial moraine deposited within the local Salisbury Plain environment. The sources of the smaller stones that form the Inner Circle and the Inner Horseshoe, known as the ‘bluestones’, are not native to the Salisbury Plain area. 

Read more: Whitby Jet, A Discussion of its Simulants

The earliest structures known in the immediate area are four or five pits, three of which appear to have held large pine totem-pole-like posts erected in the Mesolithic period, between 8500 and 7000 BC. It is not known how these posts relate to the later monument of Stonehenge but we do know that in about 2900 BC the bluestones were set up in the centre of the monument. 

Perhaps the distance over which these bluestones have been transported is the cause of man’s fascination with them, instead of the larger sarsen stones. This was addressed in 1923 by H. H. Thomas from the Geological Survey, who published a paper in The Antiquaries Journal claiming that he had “sourced the spotted dolerite component of the bluestones in hilltop rock outcrops in the High Preseli, to the west of Crymych in west Wales. Specifically, he thought that the tors on Carn Meini (also known as Carn Menyn) and Cerrig Marchogion were the likely source outcrops” (Earth Heritage, Summer 2013). 

Geology

Preseli bluestone is a metamorphosed dolerite outcropping in the Preseli Hills, known locally as Preseli Mountains, Pembrokeshire Wales. It is particularly notable for its spotted appearance in hand specimen, an effect caused by low-grade regional metamorphism during the Caledonian Orogeny. 

In thin sections the rock contains large pyroxene (augite) and altered plagioclase grains. The original igneous minerals have been partially altered to chlorite and epidote during greenschist grade metamorphism, and although large pyroxene grains remain, almost all the plagioclase has been altered. The remainder of the fine-grained matrix was also altered by metamorphism, although many igneous mineral shapes are evident. Not all of the bluestones standing today at Stonehenge, however, are spotted dolerites. Four of them are ash-flow tuffs, of rhyolitic composition. 

In order to identify the origin of the bluestones, Aberystwyth University has worked to analyse the composition of micron-sized zircon crystals from rhyolite samples from Stonehenge using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The technique focuses a very high-power laser beam onto the zircon crystals to ‘ablate’ them - essentially vaporising them. The vapour generated by this process is then analysed in the mass spectrometer, which reveals the chemistry of the zircon crystals. This was the first time zircon chemistry had ever been used to determine the provenance of archaeological material. New research by a team of scientists including researchers from University College London (UCL), University of Manchester, Bournemouth University, University of Southampton, University of Leicester, Amgueddfa Cymru - National Museum Wales and Dyfed Archaeological Trust, presents detailed evidence of prehistoric quarrying in the Preseli Hills in Pembrokeshire, helping to answer long-standing questions about why, when and how Stonehenge was built.

Read more: Getting to Grips with GemTOF Technology

They have identified the outcrop of Carn Goedog as the main source of Stonehenge’s ‘spotted dolerite’ bluestones and the outcrop of Craig Rhos-y-felin as a source for one of the ‘rhyolite’ bluestones. The special formation of the rock, which forms natural pillars at these outcrops, allowed the prehistoric quarry-workers to detach each megalith with minimal effort. Dr Josh Pollard, from the University of Southampton, said: “They only had to insert wooden wedges into the cracks between the pillars and then let the Welsh rain do the rest by swelling the wood to ease each pillar off the rock face. The quarry-workers then lowered the thin pillars onto platforms of earth and stone, a sort of ‘loading bay’ from where the huge stones could be dragged away along trackways leading out of each quarry.” 

Modern Demand

The material which has flooded the market is Preseli spotted dolerite rather than the rhyolitic material. It is fashioned primarily into large cabochons or skulls, spheres, wands and other items evoking pagan symbolisms. The bulk of the material is polished in mainland China, with elaborate carvings being worked in the Netherlands according to my source. 

The bodies that are concerned with protecting the sites of the bluestone are increasingly concerned that illegal extraction of material must be occurring due to the large quantity of material on the market. This has an implication from an archaeological point of view as these ancient sites, believed to be the Neolithic quarries from where the megaliths were extracted, may still hold clues as to Stonehenge’s history and are designated Sites of Special Scientific Interest (SSSI) and are therefore legally protected.

Having spoken to the source of the majority of rough material into the supply chain, however, I am assured that all the material currently on the market has come from his source, a farmland some 500 m outside the boundary of the SSSI. He explained to me that the source of his deposits are glacial erratics, the weathering skins of which have indicated a date of deposition circa 11,000 BC at the end of the last ice age and predating quarrying activity by some 7,000 years. The erratics are dug up from his farmland, usually five to six feet below the surface and then exported for manufacture. 

Despite this, in order to protect the bluestone quarries, it has been proposed that a worldwide ban of the sale of Preseli spotted dolerite may be required. This would be unprecedented for a non-organic gem material and raises the important question of whether (and, indeed, how) such prehistoric stone sources should be protected and conserved in the future. It also demonstrates the need for geologists, archaeologists and manufacturers to work more closely together to ensure a greater transparency regarding the sourcing of our British gem materials.

Why Preseli Bluestone? 

The new discoveries may also help to understand why Stonehenge was built. Professor Parker Pearson and his team believe that the bluestones were erected at Stonehenge around 2900 BC, long before the giant sarsens were put up around 2500 BC. So why did Neolithic man decide to use Preseli bluestone? 

A twelfth-century account of Geoffrey of Monmouth uses the myth of Merlin bringing the stones to Stonehenge and states that the stones had medicinal properties that could be accessed by washing the stones and then pouring the water into baths. The water absorbed the healing virtues of the stones. Even today, folklore in Pembrokeshire suggests that the Preseli bluestones possess healing qualities. There is yet another intriguing (and surprising) aspect to the Preseli bluestones, which is that a relatively high proportion of them (perhaps as much as 10%) have the rare property of being lithophones - ‘musical stones’. That is, they can ring like a bell or gong, or resound like a drum, when struck with a small hammerstone, instead of the dull ‘clunking’ sound rock-on-rock usually makes. 

Read more: The History of Diamonds in Engagement Rings

As gemmologists we seldom use sound when contemplating gemstones, other than the distinctive ‘chink’ of spodumene perhaps, but as a lapidary, sound is important when polishing stones. We are often subconsciously using sound for facet orientation, to listen for surface imperfections and to distinguish different hardnesses of the material we are polishing. 

The fact that lithophones are along the Carn Menyn ridge tends to suggest that sound may indeed have been an important factor in the general location being special to Neolithic people - the sounds from stones were perhaps perceived as emanating from spirit inhabitants of rock and cliff interiors. The underlying reason for the perceived importance or special nature of the bluestones by Neolithic people therefore seems to lie in the idea that Mynydd Preseli was viewed as a sacred land in that era. Could it be that deep within our psyche we still carry a connection with this ancient landscape and the desire for objects made of the bluestones is still strong within us? ■ 

This article originally appeared in Gems&Jewellery Mar/Apr 2016 / Volume 25 / No. 2 pp. 25-27

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 Stonehenge. All images courtesy of Sarah Steele.   

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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

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

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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

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

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

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

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

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 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

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

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This article by Guy Lalous ACAM EG summarises a study on the gemmological and physical properties of brown zircon from the Central Highlands of Vietnam, together with its chemical composition, Raman, Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet Visible Near InfraRed (UV-Vis-NIR) spectroscopic features. 

Zircon, zirconium silicate (ZrSiO₄) crystallises in the tetragonal system and has a high refractive index (RI), high dispersion, and subadamantine lustre. Zircon can be found in igneous, metamorphic and sedimentary rocks and is particularly common in plutonic rocks.

Are there different types of zircon?

Zircon crystals possess a range of optical and physical properties and can be classified in three types: high, intermediate and low. Zircon is quite unique in this regard. High zircon possesses the full crystal structure, there is little or no damage from radioactive elements. In intermediate zircon the radioactive elements have caused some structural damage and the physical and optical properties are in between low and high. The crystal structure of low zircon has been altered by thousands of years of irradiation from its own trace elements with extensive crystal-structure damage as a result. The optical and physical properties of the latter are lower.

What are rare earth elements?

Rare earth elements (REEs) are a group of 17 metals, comprising of the lanthanide series of elements, in addition to scandium and yttrium, which show similar physical and chemical properties to the lanthanides. The REEs have unique metallurgical, magnetic and luminescent properties. Luminescent properties are useful in gemstone determination. 

Read more: Getting to Grips with GemTof Technology

The original rock type of individual zircon grains can be reliably distinguished by taking a multivariate statistical approach, using a range of trace elements including at least hafnium, uranium, thorium, yttrium and the Heavy-REEs.

What is metamictisation?

Metamictisation of natural zircon results from accumulated radiation damage to the crystal structure caused by radioactive decay of trace amounts of urnaium and thorium, substituting for zircon. The most striking effect of metamictisation is the destruction of anisotropy.

What is the origin of colour in zircon?

In general, the colouration of zircon is affected by its trace-element composition (e.g. transition metals and REEs) and also by radiation damage (e.g. radiation-induced colour centres). Hafnium as well as radioactive elements such as U⁴⁺ and Th⁴⁺ can substitute Zr⁴⁺ in dodecahedral coordination. The resulting radiation damage to the structure results in metamict zircon. The reddish brown colour of Ratanakiri (Cambodian) zircon is thought to be due to the defect center caused by irradiation of uranium and thorium, commonly present as trace elements in its structure.

Gemmological and physical properties of the Vietnamese zircons: 

• Rough
• Prismatic
• Orangey brown to dark reddish brown in colour
• Translucent to transparent crystals
• Weak-to-distinct pleochroism.
• Hydrostatic specific gravity (SG) range from 4.10-4.60.
• Samples were inert to UV radiation

The transparent near-colourless to light-coloured samples showed typical REE-related spectroscopic features. UV-Vis-NIR of the reddish brown zircons showed a continuous increase in absorption toward the UV region, in particular between 400 and 600 nm with a shoulder at around 500 nm. The very light brown and orangey brown have a shoulder of very low intensity.

Microscopic observation of the Vietnamese zircons revealed straight and angular growth zoning. The following inclusions were identified: apatite, hematite, red iron hydroxide and ilmenite. Rare inclusions of baddeleyite, tourmaline and jadeite were reported in a previous  study.

What about Raman spectroscopy and crystallinity of zircons?

The process of metamictisation of zircon greatly influences its Raman spectrum. The crystallinity of zircons can be measured as increasing irregularities of bond-lengths, bond-angles and a general breaking-up of the structure result in changes in wavenumbers and widths of the Raman bands. Full width at half maximum is the width of the Raman spectrum curve measured between those points on the y-axis, which are half the maximum amplitude.

Raman spectra of the Vietnamese zircons showed dominant peaks at 1008;  975; 437; 392; 355; 225; 214 and 202 cm^–1. The strongest bands in the 450-350 cm^–1 range and around 1000 cm^–1 are due to internal vibrations of silicon oxide (SiO₄) tetrahedra. The most intense intra-tetrahedral vibrational band at 1008 cm^–1, is best suited to quantify the degree of metamictisation. Crystalline (high-type) zircon shows a full width at half maximum (FWHM) value of 30 cm^–1. The Raman data of Vietnamese zircon have FWHM values in the 2-3 cm^–1.

Read more: Reconstructed Amber Broken Down

FTIR spectra displayed three sharp, intense bands in the 1100-400 cm^–1 range at 854; 609 and 430 cm^-1. The intense band around 854 cm^–1 (and shoulder at 970 cm^-1) is due to internal stretching vibrations of SiO₄ tetrahedra; this band weakens and broadens in metamict zircon. The band at 609 cm^–1 (due to internal bending vibrations of SiO₄ tetrahedra) and the band at 430 cm^-1 (due to the external or lattice vibration mode) may also weaken and broaden with metamictisation, and they are nearly absent from highly metamict samples. FTIR spectroscopy of the Vietnamese zircon confirms the results of the Raman spectra showing that the samples are well crystallised.

The average chemical composition of the zircons show low contents of non-formula elements. The most abundant chemical substitution was halfnium. The total REE-oxide concentrations were 0.03-0.08 wt%. All the samples contained low amounts of thorium and uranium, and the Th:U ratios are consistent with a magmatic origin (and subsequent transport to the earth’s surface in alkali basalts). Raman and FTIR spectroscopy indicate that the zircons are high type (highly crystalline).

Read more: Exploring the Wonders of Myanmar

Heat treatment of the Vietnamese zircon under oxidising conditions produced a lighter but unstable brownish orange colour in the range of 200-500 °C and a stable pale brown colour after heating to 600 °C, whereas treatment under reducing conditions yielded a blue colour after heating to 800-1000 °C. The zircons turn blue as the small concentration of uranium within the atomic structure undergoes a change in charge. The treated blue colour was stable.

Zircon from the Central Highlands of Vietnam has similar properties and heat-treatment behaviours to those of zircon from Ratanakiri. ■ 

This is a summary of an article that originally appeared in The Journal of Gemmology titled ‘Geology, Gemmological Properties and Preliminary Heat Treatment of Gem-Quality Zircon from the Central Highlands of Vietnam’ by  Le Thi-Thu Huong, Bui Sinh Vuong, Nguyen Thi Minh Thuyet, Nguyen Ngoc Khoi, Somruedee Satitkune, Bhuwadol Wanthanachaisaeng, Wolfgang Hofmeister, Tobias Häger and Christoph Hauzenberger 2016/Volume 35/ No. 4 pp. 308-318 

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 Vietnamese zircon with an internal feature of opaque hematite and red iron hydroxide (magnified 20x). Image courtesy of N. T. M Thuyet and L. T. T. Huong.

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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

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

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

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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

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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

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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

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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

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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

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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

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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

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Everyone knows that lucky April-born souls have been blessed with one of the most prestigious birthstones: diamond. However, there is an alternative birthstone for the month and it's a 'hidden gem'... so to speak! Gem-A Member, Julia Griffith FGA DGA EG explains why rock crystal is worth your time and attention. 

Rock crystal is the purest variety of quartz and is transparent and completely colourless. Its name derives from the Greek term krustallos meaning 'ice' and it is the sister gemstone to colourful varieties of quartz, such as amethyst and citrine. 

What makes rock crystal special?

From across the spectrum of gemstones, only rock crystal offers such a wide variety of attractive inclusions. For this reason, rock crystal has the potential to be one of the most characterful and artistic gemstones for collectors and jewellery lovers alike. 

Many may think of 'inclusions' as flaws, however, when viewing the array of possible features that can be available within this gemstone one may change this opinion. There is rutilated quartz, tourmalinated quartz, fluorite in quartz, hematite in quartz, gilalite in quartz, pyrite in quartz… the list goes on! These different mineral inclusions add further variety to the rock crystal family whilst offering dozens of different looks.

Read more: Navigating Enhanced Versus Natural Lapidary Materials 

Rutile in quartz. Image courtesy of Julia Griffith.

Considering its place in the quartz family of gemstones, rock crystal has a hardness of 7 on the Mohs Scale. It is reasonably durable and stable, which makes it suitable for all kinds of jewellery pieces. It can be fashioned as carvings, cabochons or faceted gems.

Read more: The Historic Significance and Mythology of Amethyst 

An additional bonus with quartz is that it is readily available in larger sizes and at wallet-friendly prices. If you are searching for a statement pendant, beautifully-included rock crystal could be a fantastic option. 

Fluorite in quartz. Image courtesy of Julia Griffith.

The Uses of Rock Crystal

Transparent rock crystal has been used as an imitation of diamond for centuries, due to the fact they are both colourless. Rock crystal will not be as 'firey' as diamond as it does not disperse light to the same degree, however, a well-cut rock crystal can be very brilliant with excellent return of white light.

Faceted rock crystals are still used as diamond imitations today, particularly as 'accent stones' in jewellery. Designers may choose to surround a coloured stone with melee-sized rock crystals rather than diamonds, offering affordable price-points to the consumer whilst giving a similar look.

Quartz Crystal Formation

Quartz is a silica (SiO₂) and is the most abundant mineral on Earth and therefore it is mined in many localities throughout the world. Quartz grows as long prismatic crystals with pyramidal points that can occur as single crystals, clusters and geodes - all of which can be very attractive and are commonly used as display pieces or set within jewellery. The largest single crystal recorded was from Itapore, Brazil and measured over 20 feet in length and weighed over 44 tonnes.

The industrial uses for rock crystal quartz outweigh its use in jewellery. It is used within the manufacture of glass, sand, ceramics, brick and abrasives (to name a few) and it is considered one of the world’s most useful natural materials.

Understanding Synthetic Quartz

Since its successful synthesis in the 1950s, synthetic lab-grown quartz is used extensively for the majority of industrial processes and may also be found within the gem trade as fashioned stones. 

Notably, quartz is used in the mechanism of quartz watches (hence the name) and anyone who sells watches will know that quartz movements keep exceptionally accurate time losing only seconds over the life-time of the battery. This is thanks to quartz’s ability to release regular electronic impulses at precise frequencies.

This rare property, known as piezoelectricity, is utilised within our GPS equipment, telephones and radios as well as in the mechanism, which triggers the airbags in our cars.

It is this property, which is thought to be exploited during crystal healing as the energy held within rock crystal is thought to amplify and channel universal energy. Hopefully, we have managed to change your mind about rock crystal! Why not celebrate April births and special occasions with this underappreciated gemstone instead of the diamond? You may just fall in love with something new. ■

Get started on your gemstone journey with gemmology courses and qualifications from Gem-A. Find out about the Gemmology Foundation and Gemmology Diploma here. 

Do you have a passion for diamonds? Discover the Gem-A Diamond Diploma and Short Courses hereand Short Courses here. 

Cover image Tourmaline in quartz. Image courtesy of Julia Griffith.

Download PDF of Volume 35 / Issue 5 / 2017

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Point Point Point Point

Gem-A gemmology and diamond tutor Julia Griffith FGA DGA EG led a gem central titled Exploring the Differences between Glass In-filled, Flux Healed and Lead Glass-filled Ruby, in an informative and engaging gem central evening. Julia summarises the evening here for those that missed out. 

The latest Gem Central evening held on 30 April at Gem-A HQ focused around three treatments of ruby; glass in-filling, flux healing and lead glass-filling. These treatments all aim to treat fractures and/or cavities within ruby which as a result alters the transparency, apparent clarity and durability of these treated stones.

I was originally asked to discuss the topic of ruby treatments at the Institute of Registered Valuers (IRV) conference in November 2016. These treatments have been the matter of confusion and debate over the last 33 years.

Read more: From Elizabeth I to Elizabeth Taylor with John Benjamin FGA DGA

‘Surface repair’ (also referred to as ‘glass-filling’ and glass-infilling) came onto the market in 1984 but was rejected by the European market. Flux-healing flooded the trade in 1992 and dominated the market for over a decade and is still hugely prevalent in the market today. Lead glass-filling has been on the market since 2004; the starting material for which is industrial grade corundum so this treatment has hit the market in the tonnes. 

The terminology used and the aims of these treatments are all similar, however, there are significant differences, which will affect the way laboratories and traders will classify these gems. Therefore it is important for the gemmologist to understand and recognise these treatments in order to identify them correctly.

Further discussed were the treatment methods, the effect of the treatment and identification features of each treatment. Also highlighted was the cross-over between what can be classed as ‘flux-healed’ and ‘glass infilled’ and how this effects the disclosure of these treatments.

The workshop focused on the importance to being able to recognise the different identification features, disclosure and the stability of these treatments. 

Read more: Zircon from Vietnam: Properties and Heat Treatments

The Gem Central evening hopefully shed some light on these three treatments. Many visual aids were available and plenty of specimens to view.

For the first time the Gem Central evening was recorded in view of making our Gem Central talks accessible to members and students worldwide. It was a very exciting new venture to be a part of.  

I would like to express special thanks to Richard Hughes (Lotus Gemology, Christopher Smith (AGL), Henry Haenni (SSEF), Stasha Tereszczuk (David J Thomas) and Tom Stephan (DGemG) for assisting me in my research and understanding. ■

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 flux-healed rubies. Image courtesy of Julia Griffith. 

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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

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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

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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

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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

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

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

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

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 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

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

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