Jack Ogden FGA takes a look at the history of diamonds being used in engagement rings. You might be a little surprised at how far the custom dates back...

Here is a question for you. Read this sentence about engagement rings: “As for the engagement ring, modern fashion prescribes a diamond solitaire, which may range in price from two hundred and fifty to two thousand dollars.” When do you estimate that was written? Before or after World War II? 

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

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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

---

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

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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

---

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

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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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John Benjamin FGA DGA,  jewellery consultant, contributor to BBC’s Antiques Roadshow, author and historian, presented the January Gem Central at Ely Place. Angharad Kolator Baldwin reports on his fascinating lecture…

Starting his career at Cameo Corner, a jewellers previously found in Bloomsbury, John Benjamin successfully passed the Gemmology Diploma and Diamond Diploma courses at Gem-A, before joining Phillips Fine Art Auctioneers as a cataloguer and valuer. After becoming the International Director of Jewellery at Philips, he left to establish his own company, John C Benjamin Limited, an independent jewellery consultancy.

Read more: Gem-A Student Celebrates Southend Success at Houses of Parliament

John’s mission is to "inculcate people with knowledge about antique jewellery" and his talk A History of Jewellery from Elizabeth I to Elizabeth Taylor presented at Gem Central on 17 January, was certainly a splendid opportunity to bask in his extensive knowledge.

The talk began in the sixteenth century and took the audience on a journey through the centuries, showcasing examples of beautiful jewellery in paintings and photographs, demonstrating the widespread fascination the public have with pearls, diamonds and other precious stones.

Gems in the sixteenth century were believed to have prophylactic properties. Evidence has been found that suggests pearls used to be powdered and drunk as a cordial to protect against disease, while garnets were worn against the skin and said to prevent the individual from having nightmares. Similarly smallpox scars were believed to be cleansed with sapphires and peridot was believed to promote love making. Although there have been a few changes in daily practices, gemmologists today still learn the birthstones for each month and gemstones remain associated with mystical and healing properties.

Social change is also reflected in jewellery trends. The obsession at the turn of the sixteenth century with death, when people were acutely aware they were unlikely to survive over 30, and wanted to immortalise their nearest and dearest saw the fashion for Memento Mori (remember you must die) jewels. The emergence of imitation gemstones in the nineteenth century when the rate of crime was rising and rather than risk losing precious jewellery in robberies, it was better to invest in paste and keep the real items in a safe deposit box.

The audience were show a seventeenth century Dutch painting detailing a women’s jewellery box. Containing a diamond necklace and a string of pearls, the jewellery was not dissimilar to what you would find in a jewellery box today. John made the point that nothing fundamentally changes in people’s jewellery choices. Although Antwerp may have revolutionised diamond cutting, and the location of the most prolific diamond mines may have changed, our hunger to adorn ourselves to symbolise wealth and power remains.

"Jewellery follows the money", said John, whether it is the Monarch or the most popular celebrity. For centuries we have ogled the gems adorning powerful and wealthy people and sought to copy the taste of the rich and powerful, in an attempt to emulate their success.

Despite two fascinating hours, it's clear that John's Gem Central discussion barely touched the surface of his extensive knowledge of antique jewellery. As he moved around the room, the audience holding on to his every word, it was apparent that we were privy to a rare insight into the antique world of jewellery. He told us the story behind pieces, the trends of the past, and what this can tell us about the future.

Read more: Gem Central with Marcus McCallum FGA

There is "a social backdrop to jewellery trends", he informed us. Through understanding what was happening at a particular point in history, we can better understand the fashion.

When asked what he thought the jewellery of tomorrow would be…he replied ethnic jewellery. As society becomes more informed and conscientious, the public are looking for materials from sustainable sources, with a story attached. But as much now as in the past, this choice is affected by those with high status.

The audience were taken on an insightful journey through the progression of jewellery design, from Elizabeth I to Elizabeth Taylor, and had a look at the evolution of jewellery in the twentieth century. John visited many themes including Renaissance pearls, enamel, The Cheapside Hoard, mourning jewellery, the age of the faceted stone, Neo Classicism, Victorian sentiment, naturalism, souvenir jewels and the age of mass production. The broad range of topics discussed meant there was something new for everyone present.

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

Interested in finding out more? Visit Gemmological Instruments, where you can purchase John’s book, Starting to Collect Antique Jewellery instore or by contacting instruments@gem-a.com.

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

Cover image a sixteenth century Spanish enamelled gold devotional Reliquary Pendant fashioned as a Ram, the fleece studded with pearls. Image courtesy of John Benjamin. 

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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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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. 

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

---

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. 

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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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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

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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. 

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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

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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

---

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.

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

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

Amber

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

Read more: Reconstructed Amber Broken Down

Baltic amber

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

Dominican amber

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

Mexican amber 

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

Burmite 

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

Australian amber

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

Identifying Amber

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

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

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

Horn

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

Differentiating types of horn 

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

Tortoiseshell

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

Ivory

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

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

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

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

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

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

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

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

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

Cover image assortment of organic samples. Image courtesy  of Gem-A. 

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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

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

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

Birthstones Guide: Emerald for those Born in May 

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

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

Read more: The 'Emerald Desert' of Western Australia

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

Typical Emerald Inclusions 

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

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

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

 
Needle-like inclusion. Image courtesy of Pat Daly. 

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

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

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

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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

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

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

What Makes Alexandrite Valuable?

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

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

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

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

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

The Alexandrite Colour Change Effect

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

Alexandrite photographed in daylight.

Alexandrite photographed under incandescent light.

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

Read more: What Makes a Gemstone Rare?

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

Alexandrite Pleochroism

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

Alexandrite Origin

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

Another example of the colour change effect in alexandrite.

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

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

Alexandrite Synthetics

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

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

An example of synthetic alexandrite.

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

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

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

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

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

How can we classify solid inclusions?

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

What is exsolution?

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

Read more: Sri Lanka - A Gem of an Island

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

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

What is asterism?

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

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

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

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

Read more: Reconstructed Amber Broken Down

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

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

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

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

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

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

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

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

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

Rough peridot crystals. Image by Gem-A.

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

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

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

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

Mining for peridot. Image by Gem-A.

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

The History of Peridot

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

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

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

Other localities where peridot is found are Myanmar, Pakistan and the Peridot Mesa in the San Carlos Apache Native American Reservation in Arizona, USA. Recently, a major new source has been discovered and developed by Fuli Gemstones in the Changbai Mountains in Northeast China.

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

The Physical Properties of Peridot

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

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

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

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

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

Peridot Inclusions

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

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

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

Read more: How to Identify Antique Edwardian Jewellery 

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

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

Cover Image: Peridot © GemA.

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

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

Tourmaline Colours 

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

Read more: Gem-A confirms oldest known carved tourmaline

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

Parti-Colour Tourmalines 

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

Bicoloured tourmaline on quartz. Image: ©Gem-A

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

Read more: Getting to grips with multi-colour gemstones

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

Tourmaline Crystals 

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

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

Tourmaline Discovery 

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

Tourmaline Mythology

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

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

Facts about Tourmaline 

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

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

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

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

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Cover image Tourmaline group. Image courtesy of Julia Griffith.

Helen Molesworth FGA, managing director of the Gübelin Academy and a professor of the history of jewellery, takes the reader back in time to Seilam, now Sri Lanka.

'From here...we reach the island of Seilam, which is, for its size, one of the finest islands in the world...This island produces many precious gems, amongst which are rubies, sapphires, topazes and amethysts. The King of the island owns a ruby thought to be the most beautiful in the world, as long as the palm of your hand and as thick as three fingers; it shines like the most burning fire and is perfect.' - Livres des Merveilles du Monde or Book of Marvels of the World, Marco Polo, ca 1300

At the age of 17, a young merchant from a Venetian family set off with his father and uncle on an unusual expedition: to travel and explore the Far East. Twenty-four years later, in 1295, they returned to Venice, wealthy men, with a valuable hoard of both stones and stories. Immediately caught up in the Italian war to which they had returned, Marco Polo was imprisoned, and before his release, dictated his travels to a fellow inmate of posterity. What is passed down to us is a wonderful medieval European account of parts of Asia and the Middle East, from a unique historical perspective. Although relatively brief, the account of Sri Lanka, here Seilam, is extremely appropriate. It is an excellent early reference not only to the first known source of ruby (and maybe also and/or spinel, which was often confused in early sources) and sapphire at the time, but also to the beauty of the island.

A roman sapphire cameo, almost certainly from Sri Lanka, depicting Aphrodite feeding an eagle, first century. Image courtesy of the Fitzwillian Museum, Cambridge.

Known by the Greeks and Romans as Tabropane, in Persian as Serendib, and to be recognised more recently under British rule as Ceylon, Sri Lanka was often referred to by writers as a utopian land of natural riches and great beauty. The earliest gem reference to the island was as the origin for the valuable gems given by Middle Eastern King Solomon to the Queen of Sheba in the Old Testament. Centuries later, not far away in ancient Iraq, a wonderful oral tradition of fabulous story-telling developed in the Thousand and One Nights, in which we find the fantastic tales of continuous castaway Sinbad the Sailor, whose sixth voyage saw him shipwrecked on the very same island, where rivers flowed with rubies, diamond, pearls and 'many precious things'. From a western perspective, Sri Lanka's natural resources were already being traded into Europe through India by the time of Alexander the Great in the third century BC, thanks to the development of the Silk Route. By the time of Marco Polo's Livres des Merveilles du Monde, this fine island paradise was already clearly recognisable as an 'Island of Gems': the Ratna Dweepa of ancient Sanskirt.

A roman gold ring mounted with a sapphire, Sri Lankan, circa third century AD, Babar-Content Collection of Ruby, Sapphire and Spinel. Image courtesy of Medusa-art.com

All the more amazing are such early geographically-relevant accounts of sapphire when we realise that many seemingly ancient references to corundum are mistranslations or transliteration errors. Traditionally, European scholars have substituted our word (and European variations of) 'sapphire' for the ancient Latinised Greek or Persian versions of sapphirus, discarding modern day mineralogy in their translation efforts. In the majority of early references, such sapphirus would have been the blue lapis lazuli from the ancient mines of Afghanistan, and at worst case, any blue stone in general. The poor ruby suffers even worse the woes of inaccurate reporting. Often credited by non-historians today with being one of the Old Testament gemstones mounted in the High Priest's breastplate in the book of Exodus together with other marvellous ancient ruby references, in fact we have little to no archaeological evidence supporting the use of ruby as a gem so far back. Other red gems such as garnet, spinel, maybe; ruby, sadly not.

This highlights the importance of archaeological evidence supporting ancient references, and happily in the case of sapphire, a handful of important sapphires survive from antiquity. Several known Roman jewels exist, perhaps set in a ring with a single 'cabochon' polished pebble, such as the third century example from the Babar-Content Collection; and a few more tend to appear with other multi-coloured gems in later Byzantine jewels. Arguably one of the earliest and most beautiful is the Roman sapphire drilled as a bead and carved in cameo depicting Aphrodite feeding an eagle, a subject of imperial allegory from the first century and now in the Fitzwilliam Museum in Cambridge: an extraordinary important object, which would have been in the most prestigious of ancient collections.

The spoils of river mining in Sri Lanka: a collection of water worn sapphire pebbles.

By the Middle Ages onwards, naturally more sapphires survive, and unsurprisingly the best are found in royal collections. Two spectacular sapphires sit in the Imperial Crown of Great Britain: the seventeenth century Stuart Sapphire and the eleventh century St Edward's Sapphire, the oldest gem in the Royal Collection. Under Queen Victoria, both astonishing stones took pride of place at the front and atop the Imperial Crown. The huge hundred carat Stuart Sapphire sat central to the circlet, until it was bumped to the back by the Cullinan II in 1909, while the smaller St Edward's sapphire, eponymously and originally belonging to Edward the Confessor, remains in its venerated position, befitting its earliest owner, in the surmounting Maltese Cross.

Helen Molesworth trying out traditional faceting and polishing techniques with a bow drill in Sri Lanka. Image by Armil Sammoon.

Perhaps the most remarkable early medieval sapphires, however, were those mounted in the early ninth century Carolingian amulet known as the Talisman of Charlemagne. Said to have been sent to the Holy Roman Emperor by the Middle Eastern Abbasid Caliph Harould Al-Rashid, two sizeable sapphires once sandwiched a hair of the virgin as combined powerful symbols of purity, loyalty, royalty and righteousness. Exemplary too, of our Silk Route road for sapphire travels. These, and all those preceding, were almost undoubtedly examples of Sri Lankan sapphires, as Sri Lanka was, crucially, our only known source of sapphire in the ancient world.

I was fortunate enough to visit this incredible country recently, and to experience production and trade first hand on this 'Island of Gems'. Sapphires are still central, psychologically and financially, with a host of other gems, including garnet, moonstone, quartzes and spinel featuring frequently in local mining and manufacturing. I experienced main mining techniques directly, plus post production, in the regions surrounding Ratnapura, our traditional 'City of Gems', and from a historical perspective, it was remarkable to see hundreds, if not thousands, of years' practices continuing today as if through unbroken tradition.

Local miner with gem finds, Sri Lanka.

River panning for alluvial deposits continues almost unchanged, a millennial old mining practice which sorts surface-reachable deposits with relative ease. I descended shaft mines, also after secondary placers and another age old mining technique, which would have developed naturally after easier alluvial river beds would have been worked out. Watching the traditional blow-pipe heat-treatment of ruby buried amongst coke and coconut shell in a back yard reminded me of two medieval Arabic accounts - of Middle Eastern polymaths Al-Biruni and Teifashi - of burying Sri Lankan rubies within or under bonfires to improve their colour. Even some of the local cutting and polishing practices, with original hand-held bow drills, followed almost the exact same mechanism as a gem-carving drill depicted on one Mediterranean Roman gem-engraver's tomb from the first century AD.

Traditional heat treatment with blow-pipe and charcoal, Sri Lanka.

Yet Sri Lanka has balanced tradition with continual development. While quality of production and some traditional techniques have remained consistent for thousands of years, cutting-edge technologies have been developed and international trade drawn in from all over the world. At the same time as remaining a player on the world stage of gem production, Sri Lanka has successfully held off the loom of large scale mining giants ready to reap the riches of this tiny island below the surface, a forward-thinking decision in favour of local sustainable practices to give the country and its people a long term future.

This compact but competent land, long considered a natural utopia to travellers and traders, and once more coming into its own in terms of tourism, has consistently remained a true Island of Gems, a centre for sapphires, and indeed one of the 'finest islands in the world'.

Gem-A members can log in to read the full article Gems&Jewellery Autumn 2017 / Volume 26 / No. 3

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: Sapphire crystals from Sri Lanka. All images ©Helen Molesworth, unless 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.

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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. 

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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.

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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.

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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.

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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.

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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...

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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.

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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.

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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!

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

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

Topaz History and Meanings

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

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

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

Topaz Colours and Localities

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

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

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

What about Imperial Topaz?

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

Red-orange and pink tones in a single topaz crystal. Photograph by Pat Daly, Gem-A. 

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

Topaz Colour Treatments

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

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

Topaz Properties

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

Read more: Exploring the Varieties of Quartz

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

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

Topaz Inclusions

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

Read more: What Career Paths Can Trained Gemmologists Take?

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

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

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

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

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

Learn more about gemmology with our Short Courses and Workshops.

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

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

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

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

Read more: Zircon from Vietnam

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

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

Gemmology of Turquoise

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

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

Read more: Natural Vs Enhanced Lapidary Materials

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

Turquoise simulant; paste. Photo courtesy of Pat Daly.

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

The History of Turquoise

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

Read more: Exploring the Varieties of Quartz

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

Read more: Gem-A Confirms Oldest Known Carved Tourmaline

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

Map of localities where turquoise is found throughout the world.

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

Read more: Understanding Red Beryl

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

Properties of Turquoise

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

Read more: Getting to Grips with Multi-Tonal Gemstones

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

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

Turquoise Jewellery Designs

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

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

Read more: What Gemstones Are in the Beryl Family?

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

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

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

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

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