Tenacity
Brittle
Brittle
Solubility
-
-
Durability
-
-
Specific Gravity
1.792.90-2.98
1
7.18
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Fracture
Irregular/uneven
Conchoidal, ConchoidalWalter Schumann
Cleavage
Perfect on {10bar10}
Distinct on {11 2 0}, imperfect on {10 1 1}
Mohs Hardness
2.57.5-8
2
10
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Chemical Composition
Ca6(Al,Si)2(SO4)2B(OH)4(OH,O)12•26(H2O)
Be 2SiO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references