Tenacity
Very brittle
-
Solubility
insoluble
-
Durability
-
-
Specific Gravity
3.30-3.402.9-3.5
1
7.18
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Fracture
Conchoidal
Conchoidal
Cleavage
{010} perfect, {110} distinct, {100} in traces
{110} Perfect, {???} Distinct, {???} Distinct
Mohs Hardness
6.5-75.5-6
2
10
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Chemical Composition
AlO(OH)Walter Schumann , Gemstones of the world (2001) More from other references
(Mg,Fe2+ ) 2(Mg,Fe2+ ) 5Si 8O 22(OH) 2Anthony et al , Handbook of mineralogy (2001)