Tsavorite

Infobox mineral
name = Tsavorite
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formula = Ca₃Al₂Si₃O₁₂
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color = Light to deep green
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system = cubic
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fracture =
mohs = 7 - 7.5
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polish =
refractive = 1.740Bancroft, Peter [http://palagems.com/tsavorite_bancroft.htm Tsavorite] online reprint from Peter Bancroft’s classic book, Gem and Crystal Treasures (1984) Western Enterprises/Mineralogical Record, Fallbrook, CA, 488 pp., accessed online January 24, 2007]
opticalprop = Single refractive
birefringence =
dispersion = 0.028
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gravity = 3.60–3.68
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Tsavorite or tsavolite is a variety of the garnet group species grossular, a calcium-aluminium garnet with the formula Ca₃Al₂Si₃O₁₂.Gemological Institute of America, "GIA Gem Reference Guide" 1995, ISBN:0-87311-019-6] Trace amounts of vanadium or chromium provide the green color.

Green grossular had been rare until 1967, when British gem prospector and geologist Campbell R. Bridges came across a deposit of the mineral in the mountains of north-east Tanzania.Idar-Oberstein, [http://www.gemstone.org/gem-by-gem/english/tsavorite.html Tsavorite] International Colored Gemstone Association, accessed online January 24, 2007] The specimens he found were of very intense color and of high transparency. The find interested the gem trade, and attempts were made to export the stones, but the Tanzanian government did not provide permits.

Believing that the deposit was a part of a larger geological structure extending possibly into Kenya, Bridges began prospecting in that nation. He was successful a second time in 1971, when he found the mineral variety there,and was granted a permit to mine the deposit. Until 1974, the gemstone was only known to mineral specialists; in that year Tiffany and Co launched a marketing campaign which brought broader recognition of the stone.

The name "tsavorite" was proposed by Tiffany and Co president Henry Platt in honor of Tsavo National Park in Kenya. Apart from the source locality in Tanzania it is also found in Toliara (Tuléar) Province, Madagascar, but so far, no other occurrences of gem material have been discovered.

Rare in clean gems over 1 carat (200 mg) in weight, tsavorite has been found in sizes yielding up to 15 carat (3 g) stones.

References

External links

* [http://www.mindat.org/min-7836.html Mindat.org]