Garnet is not a single mineral, but describes a group of several closely related minerals. Garnets come in a variety of colors and have many different varieties. However, the most widely-known color of Garnet gemstones is dark red. When the term "Garnet" is used, it is usually connotative of the dark red form; other color Garnets are usually given more descriptive gemstone terms. The properties below are generic to all Garnets; see the specific Garnet gemstone pages for more precise details. Almandine and Pyrope are the most widely used Garnet gemstones. Though Almandine is the most common Garnet, it is usually opaque and not fit for gemstone use. Only the less common transparent dark red forms of Almandine are used as gemstones. Pyrope is especially noted for its transparency and frequent lack of flaws or inclusions. A rose-red to violet variety of Pyrope (or intermediary between Almandine and Pyrope) is known as Rhodolite, and is a very well represented in the gem trade. Spessartite is an orange to orange-red form of Garnet, and has recently increased in popularity, with several new deposits of gem grade material having been recently exploited. Grossular, the most varicolored form of Garnet, has the important gem variety of green Tsavorite, as well as orange-brown Hessonite and a yellow to yellow-green form. Andradite, the most lustrous of the Garnets, has the rare green Demantoid variety, the yellow Topazolite variety, and the black Melanite variety. Uvarovite, the rarest of the familiar garnets, is seldom found in crystals large enough to be faceted, and is the least represented of all the familiar Garnets. Color-changing Garnet is an interesting form of this gemstone that has a different color when viewed in natural and incandescent lighting. It can have several color combinations, especially brown or orange in daylight to a pink or light red in incandescent light. Garnets occasionally displays asterism in the form of four-rayed stars. However, Star Garnets are very rare, and generally occur in opaque stones with only a weak asterism effect; thus interest in Star Garnets are limited. Garnet is a very popular gemstone, and is the most well-known dark red gemstone. Red Garnet gemstones (Almandine and Pyrope) are very affordable and faceted into all types of jewerly, including necklaces, rings, bracelets, and earrings. Round cabochons of red Garnet are also popular and used in rings and bracelets. The variety Rhodolite has become a very important jewelry gemstone, and the rare green Tsavorite and Demantoid Garnets make exquisite and costly gemstones. Color Changing Garnet has sparked recent interest, and it is most often used in rings. Other forms of Garnets such as orange Spessartite, yellow Grossular and black Melanite are also used as gemstones. Garnet is the birthstone for January. There are many forms and varieties of Garnets. The six main Garnet mineral types are:
- Color-Change Garnet - Garnet that exhibits a different color in natural and artificial light. Color-Change Garnet is a intermediary mix between the Pyrope and Spessartite (though closer in composition to Pyrope), and presents a color change from a light brownish, yellowish, or greenish in daylight to a pink or purplish color in incandescent light. A few rare specimens may even have a bluish color, which is extremely rare for Garnet.
- Demantoid - Olive-green to emerald-green gem variety of Andradite Garnet.
- Gooseberry Garnet - Light green to light greenish-brown variety of Grossular Garnet.
- Hessonite - Orange to orange-brown, transparent variety of Grossular Garnet.
- Imperial Garnet - Light pink, transparent gem variety of Grossular Garnet.
- Leuco-garnet - Colorless, transparent variety of Grossular Garnet.
- Malaya Garnet - Reddish-orange form of Spessartite Garnet (or more accurately a mixture intermediary between Spessartite and Pyrope) that originates in the Umba River Valley in Tanzania and Kenya. This term is sometimes also used as a synonym for Spessartite.
- Mali Garnet - Garnet gemstone from the African country of Mali that ranges in color from green to yellow to brown (though most often a greenish-yellow). The deposit of these Garnets was discovered in Mali in 1994, and this form of Garnet is a relatively new gemstone. The scientific classification of the Mali Garnets are not clearly identified; they can be either Grossular or Andradite, though are usually an intermediary form closer in chemical structure to Grossular.
- Mandarin Garnet - Bright orange to orange-red Spessartite Garnet, usually originating from the African countries of Namibia and Mozambique.
- Melanite - Lustrous, opaque black or very dark red variety of Andradite Garnet.
- Mint Garnet - Grossular Garnet with a light-mint-green color.
- Mozambique Garnet - Red Garnet from the African country of Mozambique, which produces fine quality Garnet gemstones. Mozambique Garnet is usually Almandine, but may also be Pyrope.
- Raspberry Garnet - Raspberry-red variety of Grossular Garnet.
- Rhodolite - Rose-red form of Garnet with a light color or more purplish color than typical Garnet gemstones. It is usually an intermediary variety between Pyrope and Almandine, though more closely towards Pyrope in composition.
- Star Garnet - Form of Almandine Garnet that exhibits asterism in the form of a four-rayed star.
- Tangerine Garnet - Light orange to orange-yellow Spessartite Garnet, usually originating from the African countries of Namibia and Mozambique.
- Topazolite - Yellow to brownish-yellow variety of Andradite Garnet.
- Tsavorite - Green to emerald-green transparent variety of Grossular Garnet from Africa
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