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Hydrogrossular

A variety of grossular containing hydroxide (OH), mineralogically this covers a series between the minerals grossular and hibschite.
General Information
A variety or type of:Grossular, which is a variety of Garnet Group
Chemical Formula
Ca
 
3
Al
 
2
(SiO
 
4
)
 
3-x
(OH)
 
4x
 - where 0 < x < 1.5
Gemdat.org, Management Team (2012)
Physical Properties of Hydrogrossular
Mohs Hardness7.5 to 8
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Specific Gravity3.25 to 3.40
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Optical Properties of Hydrogrossular
Refractive Index1.710 to 1.734
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004) GreenMore from other references
Optical CharacterIsotropic
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Colour
Colour (General)Rose-red, green
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Causes of ColourGreen ("Transvaal jade"), Cr3+ in octahedral coordination. Pink, Mn3+ in octahedral coordination
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTranslucent,Opaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Crystallography of Hydrogrossular
Crystal SystemIsometric
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
Further Information
Mineral information:Hydrogrossular information at mindat.org
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