Tenacity
Brittle
Brittle
Solubility
-
-
Durability
-
-
Specific Gravity
2.57-2.662.79-2.87
1
7.18
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Fracture
Subconchoidal, Conchoidal
Conchoidal
Cleavage
Fair on {100}, poor on {001} and {010}
{010} perfect; {100} good, interrupted; {101} indistinct; {001} in traces
Mohs Hardness
7-7.55.5-6
2
10
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Chemical Composition
Mg2Al4Si5O18
NaBePO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references