Tenacity
-
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.26-3.362.59-2.60
1
7.18
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Fracture
Conchoidal
-
Cleavage
Good on {100}
{001} Perfect, {110} Distinct, {101} Distinct
Mohs Hardness
6.5-76-7
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
Be 4Si 2O 7(OH) 2Anthony et al , Handbook of mineralogy (2001)