Tenacity
-
Brittle
Solubility
-
-
Durability
-
-
Specific Gravity
2.55-2.655.85-6.15
1
7.18
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Fracture
Conchoidal
Conchoidal
Cleavage
Perfect {10 1 0}
Fair in four directions forming octahedrons
Mohs Hardness
5.5-63.5-4
2
10
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Chemical Composition
(Na,Ca,K) 8(Si,Al) 12O 24(SO 4,Cl,CO 3) 3(H 2O)Arthur Thomas , Gemstones (2009)
Cu 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references