Tenacity
Brittle
Brittle
Solubility
Soluble
-
Durability
-
-
Specific Gravity
2.972.90-2.98
1
7.18
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Fracture
Uneven
Conchoidal, ConchoidalWalter Schumann
Cleavage
None observed
Distinct on {11 2 0}, imperfect on {10 1 1}
Mohs Hardness
2.57.5-8
2
10
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Chemical Composition
Na 3AlF 6Ulrich Henn and Claudio C.
Be 2SiO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references