Physical Properties
Tenacity
-
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.26-3.361.97-2.22
1
7.18
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Fracture
Conchoidal
Conchoidal
Cleavage
Good on {100}
None
Mohs Hardness
6.5-76-6.5
2
10
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Chemical Composition
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references
SiO 2 + H 2OUlrich Henn and Claudio C.