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