Tenacity
Brittle
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.69-3.813.26-3.36
1
7.18
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Fracture
Uneven, Conchoidal to uneven, ConchoidalWalter Schumann
Conchoidal
Cleavage
Distinct on {110}, imperfect on {010}, poor on {001}
Good on {100}
Mohs Hardness
8.56.5-7
2
10
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Chemical Composition
BeAl 2 O 4
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references