Tenacity
Brittle
-
Solubility
-
-
Durability
-
-
Specific Gravity
2.57-2.663.1-3.2
1
7.18
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Fracture
Subconchoidal, Conchoidal
-
Cleavage
Fair on {100}, poor on {001} and {010}
Vitreous, pearly on cleavage
Mohs Hardness
7-7.53-4
2
10
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Chemical Composition
Mg2Al4Si5O18
(Fe2+ ,Mg,Mn2+ ) 3(PO 4) 2 · 4H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references