Tenacity
-
Brittle
Solubility
-
-
Durability
-
-
Specific Gravity
3.26-3.415.85-6.15
1
7.18
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Fracture
Fibrous, ConchoidalWalter Schumann
Conchoidal
Cleavage
Distinct on {100}, poor on {110}; parting on {001}
Fair in four directions forming octahedrons
Mohs Hardness
7-8.53.5-4
2
10
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Chemical Composition
AlAl6O3BSi3O18
Cu 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references