Tenacity
-
Brittle
Solubility
-
-
Durability
-
-
Specific Gravity
3.172.90-2.98
1
7.18
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Fracture
-
Conchoidal, ConchoidalWalter Schumann
Cleavage
None
Distinct on {11 2 0}, imperfect on {10 1 1}
Mohs Hardness
77.5-8
2
10
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Chemical Composition
Na x[Fe2+2(Al,Fe3+ )]Al 6(BO 3) 3Si 6O 18(OH) 4Anthony et al , Handbook of mineralogy (2001)
Be 2SiO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references