Garnet

Chemical Formula Garnet is a series of several different minerals with unique chemical formulas. See The chemical formula of Garnet for details.
Color Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black
Hardness 6.5 – 8.5
Crystal System Isometric
Refractive Index 1.780 – 1.889
SG 3.5 – 4.3
Transparency Transparent to translucent
Double Refraction None
Luster Vitreous; some forms adamantine or submetallic
Cleavage None. May exhibit parting.
Mineral Class Garnet
ALL ABOUT

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.

USES

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.

OTHER NAMES

Carbuncle
VARIETIES There are many forms and varieties of Garnets. The six main Garnet mineral types are:
Almandine
Pyrope
Spessartite
Grossular
Andradite
Uvarovite
The list below are more general Garnet variety names that are commonly used:
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.Garnet gemstones are not enhanced, and their colors are always natural. Treatments such as heat treatment and irradiation have proved ineffective upon the Garnet gemstones. Several synthetic Garnets are simulants of other gemstones. The most widely known synthetic Garnet is Yttrium Aluminium Garnet (YAG), Y3Al2(AlO4)3, and it is a colorless simulant of Diamond. Widely used until the 1970′s, YAG has lost its stake Cubic Zirconia as a Diamond simulant. Gadolinium Gallium Garnet (GGG), Gd3Ga2(GaO4)3 is another synthetic Garnet form. It is rarely used as a gemstone though, and is most often produced for industrial and optical uses.Garnet SOURCESSIMILAR GEMSTONES Goshenite is the white to colorless variety of Beryl. Beryl is best known for its gem varieties Emerald and Aquamarine, as well as the lesser known Heliodor and Morganite, but the variety Goshenite less frequently used as a gemstone being that it lacks the color appeal of the other varieties.
Due to the great color variations of Garnet, many other gemstones may be confused with it. In addition, many of the individual Garnet varieties can be similar to each other. View the individual Garnet gemstone pages for specific similar gemstones for each Garnet type.
See the individual Garnet gemstone pages for specific localities of each Garnet type.
Garnet-doublets are made of a colored glass bottom with a Garnet gemstone fused to the top of the stone. Garnet doublets are rarely created anymore due to the affordability of Garnet gemstones.
Garnet TREATMENTS AND ENHANCEMENTS

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