Tenacity
-
Brittle
Solubility
-
-
Durability
-
-
Specific Gravity
2.50-2.805.85-6.15
1
7.18
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Fracture
-
Conchoidal
Cleavage
Perfect
Fair in four directions forming octahedrons
Mohs Hardness
5-6.53.5-4
2
10
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Chemical Composition
Na 4(Al,Si) 12O 24Cl to Ca 4(Si,Al) 12O 24(CO 3,SO 4)Arthur Thomas , Gemstones (2009)
Cu 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references