Tenacity
Brittle
Brittle
Solubility
Soluble
-
Durability
-
-
Specific Gravity
2.755.00-5.30
1
7.18
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Fracture
Uneven, Conchoidal
Uneven, ConchoidalWalter Schumann, Conchoidal
Cleavage
Imperfect on {110}
None, may show partings on {0001} and {10 1 1}
Mohs Hardness
5.56
2
10
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Chemical Composition
(Na,Ca) 8Al 6Si 6O 24(SO 4,S,Cl) 2Ulrich Henn and Claudio C.
Fe 2O 3Arthur Thomas , Gemstones (2009)