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Hydrogrossular

 
Wikipedia: Hydrogrossular
Hydrogrossular
General
Category Silicate mineral
Chemical formula Ca3Al2(SiO4)3-x(OH)4x
Identification
Color green to bluish green, pink, white, gray
Crystal habit Massive
Crystal system cubic
Cleavage none
Fracture conchoidal
Mohs scale hardness 7 - 7.5
Luster vitreous
Specific gravity 4.15 (+.05, -.03)
Polish luster vitreous to subadamantine
Optical properties Single refractive, anomalous aggregate reaction
Refractive index 1.810 (+.004, -.020)
Birefringence none
Pleochroism none
Ultraviolet fluorescence inert
Absorption spectra dark green hydrogrossular often shows cutoff below 460nm. Other color stones may show line around 463nm, indicating some idocrase content
References [1]

Hydrogrossular, is a calcium aluminium garnet series (formula: Ca3Al2(SiO4)3-x(OH)4x, with hydroxide (OH) partially replacing silica (SiO4)) between the grossular and hibschite endmembers.[1] Hydrogrossular is found in massive crystal habit, sometimes grown in with idocrase.[1]

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.[1] It has similarites to jade, and has the misnomers Transvaal jade, and African jade.[1]

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.[1]

External links

References

  1. ^ a b c d e f Gemological Institute of America, GIA Gem Reference Guide 1995, ISBN 0-87311-019-6



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Silicate minerals
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