Tenacity
Very brittle
-
Solubility
insoluble
-
Durability
-
-
Specific Gravity
3.30-3.402.50-2.80
1
7.18
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Fracture
Conchoidal
-
Cleavage
{010} perfect, {110} distinct, {100} in traces
Perfect
Mohs Hardness
6.5-75-6.5
2
10
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Chemical Composition
AlO(OH)Walter Schumann , Gemstones of the world (2001) More from other references
Na 4(Al,Si) 12O 24Cl to Ca 4(Si,Al) 12O 24(CO 3,SO 4)Arthur Thomas , Gemstones (2009)