Tenacity
Brittle
Brittle
Solubility
Soluble
insoluble in water
Durability
-
-
Specific Gravity
2.975.00-5.20
1
7.18
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Fracture
Uneven
Uneven, Conchoidal, ConchoidalWalter Schumann
Cleavage
None observed
Indistinct on {001}; partings on {011} and {111}
Mohs Hardness
2.56-6.5
2
10
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Chemical Composition
Na 3AlF 6Ulrich Henn and Claudio C.
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references