Demantoid: Not Easy Being Green
Another rare and beautiful gemstone associated with Russia is demantoid garnet: a fiery green garnet once mined only in Russia's Ural Mountains, where it was discovered in 1868. A new source was found in 1998 in Namibia, southern Africa, but it is still quite rare. Generally, Russian origin adds to the value of the material.

Demantoid garnet has a fiery brilliance not usually associated with garnets: in fact it has a higher dispersion than diamond. But all this fire and brilliant green color has a price: demantoid is the rarest of garnets, and is rarely found in sizes above a few carats.

When judging demantoid, look for the purity and intensity of the green color. Generally, demantoid jewelry is set with many small stones: large sizes are extremely rare. Collectors should always be on the lookout for Victorian jewelry set with small brilliant green stones, which could be demantoid. If they are, they add dramatically to the value of the piece. One indication of a lucky find would be a brilliance not seen in other green gemstones.

Demantoid garnets from Russia sometimes have byssolite inclusions, a form of asbestos. These fibers sometimes form a beautiful pattern like the tail of a horse, so they are called "horse-tail" inclusions. Demantoids with prominent horse-tail inclusions are particularly valued by some collectors: this is an example of an inclusion that adds rather than detracts from the value of a gemstone.