Tenacity
-
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.26-3.363.19-3.56
1
7.18
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Fracture
Conchoidal
Uneven, Conchoidal
Cleavage
Good on {100}
{110} Perfect, {010} Indistinct
Mohs Hardness
6.5-75.5-6
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
(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al) 2O 6Anthony et al , Handbook of mineralogy (2001)