Tenacity
Brittle
Brittle
Solubility
-
-
Durability
-
-
Specific Gravity
2.33-2.375.00-5.30
1
7.18
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Fracture
Uneven
Uneven, ConchoidalWalter Schumann, Conchoidal
Cleavage
Perfect on {001}, imperfect on {110}
None, may show partings on {0001} and {10 1 1}
Mohs Hardness
4.5-56
2
10
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Chemical Composition
(K,Na)Ca4Si8O20(F,OH)•8(H2O)
Fe 2O 3Arthur Thomas , Gemstones (2009)