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The Garnet family of minerals is one of the most interesting to study. A singly refractive stone, garnets occurs in a variety of colors except blue.Each specie share similar structure but vary in chemical composition and properties. The chemical formulas are given below: Uvarovite:Ca3Cr2Si3O12 Grossular:Ca3Al2Si3)O12 Andradite:CaFe2Si3O12 Pyrope:Mg3Al2Si3O12 Almandine:Fe3Al2Si3O12 Spessartine:Mn3Al2Si3O12 Goldmanite: Ca3V2Si3O12 Hydrogrossular:Ca3Al2(SiO4) Because of the very complex nature of garnet, chemical analysis is often needed to positively identify the species.
In the jewelry world, the green garnets are highly prized for its inherent beauty and also for its rarity. Tsavorite, the gem promoted by famed American jewelry firm Tiffany, is perhaps the most famous and popular and as a result also the most expensive. It has an intense deep tp medium green and a "clean" luster. It can be separated from another green variety known as demantoid garnet by looking at the facet junctions and corners for spectral colors as demantoids are highly dispersive and can be separated visually by the keen eyed. Hydrogrossulars are also occuring in green and pink hues but they are almost always translucent and seldom have transparency necessary of a facetted gem. Sometime a good green hydrogrossular maybe confused with the highest quality jade especially when the gem is in a closed mounting.
Grossular garnet are sometime pale in colors ranging from colorless to white, gray, green, greenish brown, orangy, yellow, brown, grayish black and black. Spessartite garnets are also among the most attractive with the "Mandarin" orange and some with golden yellow or whisky yellow hues. Those originating from the Umba Valley in Tanzania are called the Malaya garnet and display shades of orange, orange red, peach,and pink. Pyrope almandite are red purple hues and cut be extremely attractive. Large crystals ehich are clean and not dark are rare and can be a hundred dollars per carat for a gemmy piece.
Most garnet are a few dollars per carat and some only a few cents when they are dark or lifeless. These lower qualities garnets are used in antique Victorian stlyed jewelry and finding a following from time to time. Spessartite garnet from Sri Lanka and Burma are also a rare collectors' item with prices exceeding that of its Africa counterparts of similar color and quality. Some garnets display chatoyancy and/or color change effect additional premium to the stones' values. All in all, garnet are a most interesting gem group to start your collection as there are endless varieties, types and sources. |
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