Demantoid

General Information and Characteristics of Demantoid

• Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals.
• The chemical formula of demantoid is Ca(SiO) with chromium substitution causing the green color.
• It has a hardness of 6.5-7.0 on the Mohs scale.
• The specific gravity of demantoid is 3.84.
• Demantoid has an adamantine luster and a refractive index of 1.880-1.889.
• Demantoid is always primarily green, ranging from a strong yellowish green to nearly the color of a fine emerald.
• Some stones may have a brownish cast due to iron impurities.
• Demantoid has a high dispersion, visible as rainbow-colored flashes of light.
• The luster of demantoid is adamantine.
• Finished demantoid stones are generally under 1 carat, with stones over 2 carats being rare.

History of Demantoid

• Demantoid was discovered in 1868 in Russia's Ural Mountains.
• The gem material was found in an alluvial deposit near the village of Elizavetinskoye.
• Miners compared demantoid to diamond due to its high brilliance and dispersion.
• Demantoid became popular in Russia and was used in jewelry by Peter Carl Fabergé.
• In the 1970s and 1980s, more stones were found in the Bobrovka River, and limited production occurred in the central Ural Mountains around 1999.

Horsetails in Demantoid

• Russian demantoids often contain horsetail inclusions of chrysotile, a type of asbestos.
• Horsetail inclusions are feathery golden threads that resemble the tail of a horse.
• These inclusions are diagnostic for natural demantoid and are not found in any other green gemstone.
• Horsetails are regarded as desirable features in demantoid, indicating prestigious Russian origin.
• Some demantoids from other locations may also contain horsetails, characteristic of a serpentinite origin.

References and Resources for Demantoid

• Idar-Oberstein is a source of demantoid.
• Shipley's Dictionary of Gems and Gemology provides information on demantoid.
• The Gemological Institute of America (GIA) has grading reports and research resources on demantoid.
• The International Gem Society offers information on demantoid garnet value, price, and jewelry.
• Various articles and studies published in Gems & Gemology provide insights into demantoid, including its inclusions and origins.

Importance and Value of Demantoid

• Demantoid is highly sought after by collectors and gemstone enthusiasts.
• It is considered one of the most valuable garnet varieties.
• Its high dispersion gives it a unique sparkle.
• Demantoid is often used as a centerpiece in fine jewelry.
• The scarcity of high-quality demantoid specimens contributes to its high market value.

Demantoid Data Sources