Understanding Play of Colour and Patterns in Opal Gemstones
Did you know the colours and patterns in an individual opal gemstone can drastically alter its value and desirability? Here, Gem-A Gemmology and Diamond Tutor, Charles Bexfield FGA DGA EG offers an overview of the play of colour and patterns to look out for in the finest opal gemstones. Opal is an amorphous hydro-silicate SiO2·H2O […]
What Does It Mean When a Specimen Is Opalised?
Senior Gemmology Tutor Pat Daly FGA DGA explores the phenomenon of opalisation, how it occurs and where you can expect to find opalised specimens. Most gem quality opal forms in sedimentary rocks, as it does in Australia, for example. Many of these were marine or lake sediments within which shells, bones and wood were sometimes […]
What is the Indian Style in Art Deco Jewellery?
From beautiful carved gemstones to cultural inspirations, the Indian style in Art Deco jewellery reflects a fascination with global cultures during the 1920s and 1930s. Here, Sarah Duncan, head of the jewellery department at London-based Chiswick Auctions, offers a beginner’s guide to the Indian style in Art Deco jewels, presenting some helpful insights for anyone […]
The Unusual History of Caesar’s Ruby
Gem-A Member Jan Asplund FGA DGA explores the fascinating history of ‘Caesar’s Ruby’ – a 255.75ct gemstone that has been regarded for centuries and traded among French, Russia and Sweden since the late 16th century. Caesar’s Ruby is a piece of jewellery well known to anyone with a special interest in the history of the […]
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. Obsolete and largely forgotten jewellery books are a rare and desirable resource for jewellery historians since they […]
Top 5 Most Famous Diamonds for Gemmologists
Although all diamonds are special, there are some that are historically significant, spectacularly large and hugely important for gemmological research. Here, Rona Bierrum FGA DGA EG pinpoints the five diamonds that stand out from the crowd for gemmologists the world over. Type into any internet search device ‘Famous Diamonds’, and a litany of posts will appear, each […]
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. Silicon is the second most abundant chemical element in the earth’s crust after oxygen. The two elements combine to create […]
Understanding Iridescence in Gemstones
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. What is Iridescence? […]
Hidden Treasures: Highlights of Gem-A’s Gemstones and Minerals Collection
Locked away in the vaults of Gem-A HQ in London is an assortment of breath-taking treasures that form Gem-A’s Gemstones and Minerals Collection. Here, Gem-A Gemmology Tutor, Pat Daly FGA, offers us a glimpse at some of the more unusual items in the collection. Decades of collecting, bequests and acquisitions have led to the creation […]
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 certain 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. […]
