Russian Demantoid — Ural Andradite with the Horsetail Inclusion
Russian Demantoid — Ural Andradite with the Horsetail Inclusion
The original demantoid source, prized for chromium-driven green and the diagnostic byssolite inclusion
Russian demantoid is the trade name for chromium-coloured andradite garnet from the Ural Mountains, the original commercial source of the species and still the source against which all other demantoid is measured. The variety was discovered along the Bobrovka River in the central Urals in the 1860s and reached its first commercial peak in late-Imperial Russia. Production lapsed after the 1917 Revolution, was revived intermittently through the Soviet period, and has resumed at modest scale since the 1990s. Russian demantoid commands a meaningful premium over Namibian, Madagascan, and Iranian material on the strength of three things: the chromium-driven green, the dispersion that gives the species its name, and the diagnostic horsetail inclusion.
Composition and optical properties
Demantoid is the green chromium-bearing variety of andradite garnet, Ca3Fe2Si3O12. Hardness is 6.5 to 7, refractive index is 1.880 to 1.889, and specific gravity ranges 3.82 to 3.85. The defining optical property is dispersion at 0.057 — higher than diamond at 0.044 — which produces the strong fire visible in well-cut stones in incandescent light. Russian rough is typically yellowish-green to pure green, with the finest stones approaching emerald hue without the bluish cast of Colombian emerald. Saturation drops as iron content rises and chromium content falls; Namibian and Madagascan stones tend toward yellower body colour for this reason.
Russian demantoid is rarely treated. Heat treatment can remove brown overtones in some material but is not consistently applied; most commercial Russian rough is sold untreated, and laboratory reports for high-end stones routinely note no detected treatment.
Horsetail inclusions
The horsetail is a radiating spray of fine fibrous byssolite (a chrysotile-type asbestos mineral) found in andradite garnet from serpentinite-hosted deposits. The inclusion is diagnostic of demantoid from serpentinite host rocks and is essentially restricted in commercial gem material to the Russian (Ural), Iranian, and Italian sources. African demantoid from skarn deposits — Namibia and Madagascar — does not produce horsetails. A well-formed horsetail in a Russian demantoid is treated as a positive feature in pricing rather than a clarity penalty, in contrast to inclusions in most other gem varieties. The Gübelin Photoatlas and GIA reference literature document horsetails as confirmation of Russian or Iranian origin.
Historic and current production
The classic deposits are the Bobrovka and Poldnevaya rivers in the central Urals, with later production from the Sysert' area. Imperial-era stones reached the Russian court and the European trade through Saint Petersburg jewellers; Fabergé set demantoid widely in late-nineteenth-century jewellery. Production fell sharply after 1917 and remained limited through the Soviet period. Russian production resumed in the 1990s under various private operators; modern Russian demantoid reaches the trade through Yekaterinburg and Moscow dealers, then through European and American specialist channels.
Production figures are not transparent. Stones over two carats are rare; over three carats they enter the collector market; over five carats they are exceptional and command auction-grade pricing. Late-Imperial Fabergé-era stones with documented provenance occupy a separate price tier and trade primarily in Russian-art and high jewellery sales.
In the trade
Demantoid pricing is sensitive to origin in a way that few coloured stones are. A Russian demantoid with a strong chromium green and a clear horsetail trades at thirty to one hundred percent above an equivalent Namibian stone of similar size, colour, and clarity. Origin reports from GIA, Gübelin, SSEF, or AGL are routine for stones above one carat at the high end of the market. The horsetail is the most reliable single feature, but origin determination relies on combined microscopic, spectroscopic, and trace-element data — chromium-to-iron ratios, vanadium content, and inclusion suite together support a confident attribution.
Hardness at 6.5 to 7 supports careful daily wear in protected ring settings. We bezel-set demantoid by preference in ring designs, and use prong work for pendants and earrings where impact risk is lower.
Identification
Refractive index over the limit of standard refractometers (1.880+ requires a high-RI fluid or contact-loaded measurement), chromium absorption in the spectroscope, and the horsetail inclusion together identify Russian demantoid without ambiguity in most cases. Separation from chrome-rich tsavorite and from chrome diopside is straightforward on RI and SG alone. Synthetic andradite has been produced experimentally but is not a commercial concern in 2026.