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The world renound ruby mines at Mogok, Burma

The sapphire mines at Bang Kacha, Chanthaburi, Thailand.

Gem mining at Pailin, Cambodia.

Sapphire mining at Bo Ploi, Kanchanaburi, Thailand

Ruby mining at Bo Rai, Trat, Thailand.

The marble village of Sagyin, Shan State, Burma.

Demantoid Garnets

A parcel of Russian demantoid garnets.

Demantoid Garnets

 

Demantoid Garnet - A Stunning Vivid Green Gem  ...

Demantoid - a rare and highly prized gem by collectors and connoisseurs the world over. Demantoid is the green variety of andradite garnet (Ca3 Fe2 Si3 O12), a gem which possesses a dispersion that can surpass that of diamonds. Some demantoids show a full rainbow of spectral colours as they sparkle in the light. The relatively high refractive index of 1.881-1.888, ensures demantoid has strong brilliance and together with the unique dispersion, they have a diamond like appearance from which their name derives.

 

Demantoids are found in a variety of places but the principle and most important deposit is along the Bobravka River in the Ural Mountains of Russia. This famous deposit was first discovered in 1868 and demantoids soon became a favourite gem of the Russian Tsars. Carl Fabergé, Russia’s most famous jeweller, also used demantoids extensively. The West soon caught on to demantoids and its popularity and value grew. There are many fine examples of demantoids found in antique Victorian jewellery. Mining activity decreased during the First World War and the Bolshevik Revolution. It remained sporadic during the Soviet era but in recent years mining activity has increased and we are beginning to see this beautiful green gemstone re-emerging onto the markets.

Horsetail inclusions in demantoid garnet

Horsetail Inclusions

Horsetail Inclusions in demantoid garnet.Horsetail Inclusions

 

Along with the Russian mines, demantoids are also found in Madagascar, Namibia & Italy plus a few other minor deposits but to a lesser extent than in the Urals. The Russian stones are considered to be superior in quality and posses a unique golden yellow inclusion of byssolith needles, known as 'horsetail inclusions'. There are collectors & dealers who look for this inclusion in demantoids and hence a beautiful well-formed clear, pronounced horsetail can actually enhance the demantoid's value. The horsetail inclusion is unique to demantoids and thus a diagnostic feature to the stone's identity. Some demantoids are heated to enhance colour.

 

The ideal colour for a demantoid would be as close to a fine 'emerald green' as possible. The colour can vary from the emerald green through to an olive green colour to a green/yellow. The best dispersion is seen best in the less saturated gems. Our colour grading system is shown here with a description for each colour.

Colour grades of demantoid garnets
(1) Emerald Green   (2) Apple Green 

(3) Salad Green  (4) Olive Green

(5) Lemon Green

 

 

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