Uvarovite Garnet - Rarest of all garnets
The garnet family is one of the largest in the gemstone world. All of the different types of garnet share a common crystal structure, but varieties are distinguished according to slight differences in chemical composition.
Six common varieties of garnet are recognized according to their chemical composition. They are pyrope, almandine, spessartite, grossularite, uvarovite and andradite. There are also some mixed members, such as rhodolite garnet, which is a mixture of pyrope and almandite by composition.
A number of these varieties are fairly rare, particularly tsavorite (chrome green grossularite garnet) and demantoid (a type of andradite garnet with outstanding dispersion).
Although these are quite rare, many gem dealers are likely to have some of them in stock. An even rarer variety is uvarovite, which can be hard to find anywhere.
Uvarovite is composed of calcium chromium silicate, and is thus distinguished from both grossularite (calcium aluminum silicate) and andradite (calcium iron silicate). It was first discovered in 1832 by Germain Henri Hess (1802-1850), a Swiss-born Russian chemist, doctor and mineralogist. Hess named it after Count Sergei Semenovitch Uvarov (1765-1855), a Russian statesman, amateur mineral collector and President of the Russian Academy of Sciences from 1818 to 1855. Hess later had a mineral named after him as well - silver telluride was named hessite in his honor as a result of his important analytical work on it.
Uvarovite is the only consistently green (idiochromatic) garnet species, with a striking emerald-green color. Specimens of uvarovite are much sought after by collectors for their outstanding brilliance and color. However, it is rarely found in gemstone quality. It is usually found associated with chromium ores in Spain, Russia, and Canada. It also occurs in Finland, Norway and South Africa.
Though uvarovite crystals of reasonable size do sometimes occur in chromite and serpentine deposits, they are generally opaque. Very rarely, a tiny portion of a crystal will be sufficiently transparent to produce a small gemstone. Therefore, this type of garnet would not be listed as a gem-quality garnet if it wasn't for one major source in the Ural Mountains of Russia that yields lovely uvarovite drusy. Drusy is tiny to minute crystals that are deposited on a matrix (host rock) surface. Uvarovite drusy, like all drusy materials, is more fragile than a faceted or cabochon gemstone. Therefore, reasonable care is needed in setting and wearing such material, to prevent crushing or dislodging the tiny crystals that adhere to the matrix.