Tenacity
Brittle
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.7-3.82.69-2.79
1
7.18
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Fracture
Subconchoidal, Conchoidal
Conchoidal
Cleavage
Distinct on {010}
Poor on {0001}
Mohs Hardness
7-7.55.5-6.5
2
10
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Chemical Composition
(Fe,Mg,Zn) 2Al 9(Si,Al) 4O 22(OH) 2Ulrich Henn and Claudio C.
KNa 2(Fe3+ ,Mn3+ ,Al) 2Li 3Si 12O 30Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references