The garnet family is one of the largest in the gemstone world. All 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 based on 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 (a chrome green grossularite garnet) and demantoid (a type of andradite garnet with outstanding dispersion). But many gem dealers will have some stock in these. An even rarer variety is uvarovite, which can be hard to find anywhere.
Uvarovite is a 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 (or 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 Quebec, 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. Only rarely will a tiny portion of a crystal be sufficiently transparent to cut a small gem. This type of garnet, therefore, would usually not be included in lists of gem garnets if it weren't for one major source area in the Ural Mts. of Russia that yields lovely Uvarovite drusy. Drusy is tiny to very tiny crystals that are deposited on a matrix surface. Uvarovite drusy, as with all drusy materials, is more fragile than a faceted or cabochon gem of its species. Reasonable care is needed in setting and wearing to prevent crushing or dislodging the tiny crystals adhering to the matrix.