Hydrogrossular

Infobox mineral
name = Hydrogrossular
category = Mineral Series
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formula = Ca₃Al₂(SiO₄)_3-x(OH)_4x
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color = green to bluish green, pink, white, gray
habit = massive
system = cubic
twinning =
cleavage = none
fracture = conchoidal
mohs = 7 - 7.5
luster = vitreous
polish = vitreous to subadamantine
refractive = 1.810 (+.004, -.020)
opticalprop = Single refractive, anomalous aggregate reaction
birefringence = none
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pleochroism = none
fluorescence= inert
absorption = dark green hydrogrossular often shows cutoff below 460nm. Other color stones may show line around 463nm, indicating some idocrase content
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gravity = 4.15 (+.05, -.03)
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Hydrogrossular, is a calcium aluminium garnet series between the species Grossular and Hibschite Ca₃Al₂(SiO₄)_3-x(OH)_4x, with hydroxide (OH) partially replacing silica (SiO₄).Gemological Institute of America, "GIA Gem Reference Guide" 1995, ISBN 0-87311-019-6] Hydrogrossular is found in massive crystal habit, sometimes grown in with idocrase.

Hydrogrossular is translucent to opaque, and found in green to bluish green, pink, white, and gray. The cause of the green color is chromium, and possibly iron. Pink hydrogrossular is caused by the presence of manganese. Hydrogrossular may have dark gray to black small inclusions. It has similarites to jade, and has the misnomers "transvaal jade", and "african jade".

Hydrogrossular is sometimes used as a gemstone, being cabochon cut, or made into beads. Sources for green and pink hydrogrossular are South Africa, Canada, and the US. White hydrogrossular is sourced from Burma and China.

External links

* [http://www.mindat.org/show.php?id=1974 Mindat page about hydrogrossular]

References