Demantoid is the green variety of the Garnet species known as Andradite while Garnets are the birthstones of January. Demantoids are the rarest and most expensive kind of Garnet. Compared across other coloured gemstones, it is also one of the rarest and has one of the greatest brilliancies (comparable to Diamonds). This is also the reason why Demantoid is named after the French word demant, which means Diamond.
History & Lore
Demantoids above 1 ct are rarely seen, they are exceptionally rare above 3 cts, such stones are mostly found only in hands of big dealers and collectors. The largest Demantoid is from the Russian Ural Mountains, weighing a tremendous 252.5 cts. One of the biggest and most beautiful Demantoid is a 11.24 cts piece on display at the Smithsonian Intitution. This is highly sought after by collectors for its Vivid intense emerald-green colour and Russian heritage. Demantoids are also famous for being used in the jewellery of Peter Carl Faberge made for Tzars of Russia.
In our inventory, we have kept a pair of Russian vivid green eye-clean Demantoid earrings. It is one of our favourite collector's investment gems that we acquired a while back and fashioned into classic styled earrings.
Demantoid colours range from yellowish green to green. Russian Demantoids generally have a stronger green colour opposed to those found in other origins and carry a much heftier price tag to it. Demantoids exhibit strong fire, although it will sometimes be masked by their strong green body colour. Although a vivid green is often more desired by the market, Demantoids that exhibit stronger fire in yellowish green stones are also popular and based on the personal preference. However, Russian vivid green Demantoids still has significantly higher price differences with Demantoids from other origins, however brilliant the others may be.
Demantoids might be the only gemstone where inclusions are considered desirable and may even fetch a higher price. A unique inclusion known as horse-tail inclusion, is a characteristic of Russian Demantoids, even though it is not definitive. Hence, if a horsetail inclusion is present in the gemstone, it is highly likely that the stone is from Russia, and this would command high prices. Aside from that, Demantoids are usually clean or may contain some small crystals.
Originated from the Ural Mountains of Russia, Demantoids are now also found in Madagascar, Namibia, Italy and Iran. Russian produced Demantoids are still the most valuable and desired gemstones in the market. The 2014 auctions at Bonhams has seen a 6.83 cts Russian no heat Demantoid being hammered for a total of USD 125,000, nearly USD 20,000 per ct, which is even higher than some diamonds at the same size.
Demantoids might be heated at low temperature that may or may not enhance its colours, such treatments are stable and undetectable.
Demantoids have never been synthesized, however, many imitations still exist. Imitations includes glass and man-made gemstones such as YAG.
With a Mohs scale rating of 6.5-7, Demantoids can be durable gemstones for jewellery but it must be carefully stored and taken care of, as its more likely to be scratched than harder gemstones. Cleaning of Demantoids should only be done with warm soapy water and a soft brush.