JewelStruck Blog

Here we are, with another post in Gemstone Each Month Series (GEMS) on Garnets, for the month of January. We did some research on the mines and types of garnet, would be discussing the same in this post.

Garnets are usually mistaken as a single gem, but it is actually a family of gems. They are found all over the world including Latin America, Africa, India, Australia, Asia and some parts of Europe. The most common color of garnets is reddish brown whereas the most prized garnet is an emerald green variety called demantoid and is a member of the adradite group. Garnets are many a times found in the streams where metamorphic rock has eroded and left crystals for collection.

Pendant in uvarovite, a rare bright-green garnet

Types of Garnet used as gems are –

• Pyrope – (from the Greek pyrōpós meaning “fire-eyed”) is red in color and chemically a magnesium aluminium silicate, though the magnesium can be replaced in part by calcium and ferrous iron. The color of pyrope varies from deep red to almost black. Transparent pyropes are used as gemstones. A variety of pyrope from Macon County, North Carolina is a violet-red shade and has been called rhodolite, from the Greek meaning “a rose.” In chemical composition it may be considered as essentially an isomorphous mixture of pyrope and almandine, in the proportion of two parts pyrope to one part almandine. Pyrope is an indicator mineral for high-pressure rocks.

• Almandine –  sometimes incorrectly called almandite, is the modern gem known as carbuncle. The name Almandine is a corruption of Alabanda, a region in Asia Minor where these stones were cut in ancient times. Chemically, almandine is an iron-aluminium garnet, the deep red transparent stones are often called precious garnet and are used as gemstones (being the most common of the gem garnets).

• Spessartine – Spessartine or spessartite is manganese aluminium garnet. Its name is derived from Spessart in Bavaria. It occurs most often in granite pegmatite and allied rock types and in certain low grade metamorphic phyllites. Spessartine of an orange-yellow is found in Madagascar. Violet-red spessartines are found in rhyolites in Colorado and Maine.

• Grossular – Grossular is a calcium-aluminium garnet, though the calcium may in part be replaced by ferrous iron and the aluminium by ferric iron. The name grossular is derived from the botanical name for the gooseberry, grossularia, in reference to the green garnet of this composition that is found in Siberia. One of the most sought after varieties of gem garnet is the fine green grossular garnet from Kenya and Tanzania called tsavorite. This garnet was discovered in the 1960s in the Tsavo area of Kenya, from which the gem takes its name.

• Andradite – is a calcium-iron garnet, is of variable composition and may be red, yellow, brown, green or black. The recognized varieties are topazolite (yellow or green), demantoid (green) and melanite (black). Andradite is found both in deep-seated igneous rocks like syenite as well as serpentines, schists, and crystalline limestone. Demantoid has been called the “emerald of the Urals” from its occurrence there, and is one of the most prized of garnet varieties. Topazolite is a golden yellow variety and melanite is a black variety

• Uvarovite – Uvarovite is a calcium chromium garnet. This is a rather rare garnet, bright green in color, usually found as small crystals associated with chromite in peridotite, serpentinite, and kimberlites. It is found in crystalline marbles and schists in the Ural mountains of Russia and Outokumpu, Finland. Uvarovite crystals are generally too small to facet and are left attached to a matrix and incorporated into jewelry.

So those were the six major types of Garnets. Hope you got enjoyed reading this post, if you would like to contribute or share anything on Garnets do email us at info@jewelstruck.com.

References – Wiki