Tenacity
Brittle
Brittle
Solubility
-
insoluble
Durability
-
-
Specific Gravity
2.7-3.36.86-7.03
1
7.18
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Fracture
Uneven, Even
Subconchoidal, Uneven, Conchoidal, Irregular
Cleavage
Perfect on the {001}
{100} imperfect, {110} indistinct; partings on {111} or {011}
Mohs Hardness
2.5-3.06-7
2
10
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Chemical Composition
K(Mg,Fe++)3[AlSi3O10(OH,F)2
SnO 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references