GARNET
Garnet is a group of minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet gemstones are most often seen in red, but are available in a wide variety of colors spanning the entire spectrum. The name "garnet" comes from the Latin granatus ("grain"), possibly a reference to the Punica granatum ("pomegranate"), a plant with red seeds similar in shape, size, and color to some garnet crystals.Six common varieties of garnet are recognized based on their chemical composition. They are pyrope, almandine, spessartite, grossular (varieties of which are hessonites or cinnamon-stone and tsavorite), uvarovite and andradite. The garnets make up two solid solution series; 1. pyrope-almandine-spessarite and 2. uvarovite-grossular-andradite.The garnet gemstone is found in many colors including red, orange, yellow, green, blue, purple, brown, black, pink and colorless. The rarest of these is the blue garnet, discovered in the late 1990s in Bekily, Madagascar.Because the chemical composition of garnet varies, the atomic bonds in some varieties are stronger than in others. As a result, the mineral shows a range of hardness on the Mohs scale of about 6.5 to 7.5. The harder varieties, like almandite, are often used for abrasive purposes.
Almandine - sometimes called Almandite, is the modern gem known as Carbuncle (though originally almost any red gemstone was known by this name). The term "carbuncle" is derived from the Latin meaning "little spark." The name Almandine is a corruption of Alabanda, a region in Asia Minor where these stones were cut in ancient times. The deep red transparent stones are often called precious garnet and are used as gemstones (being the most common of the garnet gem stones ). Almandine occurs in metamorphic rocks like mica schists, associated with minerals such as Staurolite, Kyanite, Andalusite, and others. Almandine has nicknames of Oriental garnet, Almandine Ruby, and Carbuncle.
Pyrope from the Latin pyropos means similar to fire. The color of pyrope varies from deep red to almost black.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." Pyrope has trade names some of which are misnomers; Cape ruby, Arizona ruby, California ruby, Rocky Mountain ruby, and Bohemian garnet from the Czech Republic. Another intriguing find is the blue color change garnets from Madagascar, a Pyrope Spessartine mix. The colour of this blue garnet stone is not like sapphire blue in subdued daylight but more reminiscent of the grayish blues and greenish blues sometimes seen in Spinel.
Spessartite or spessartine 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. Spessartite garnet of a beautiful orange-yellow is found in Madagascar (see Mandarin garnet). Violet-red Spessartites are found in rhyolites in Colorado and Maine.
Andradite - is a calcium-iron garnet and is of variable composition and may be red, yellow, brown, green or black. The recognized sub varieties are topazolite (yellow or green), demantoid (green) and melantite (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.
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. Other shades include cinnamon brown (cinnamon stone variety), red, and yellow. Because of its inferior hardness to zircon, which the yellow crystals resemble, they have also been called hessonite from the Greek meaning inferior. Grossular is found in contact metamorphosed limestones with vesuvianite, diopside, wollastonite and wernerite.
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.
Uvarovite is a calcium chromium garnet. This is a rather rare bright green garnet, 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.
