Tenacity
-
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.26-3.413.1-3.2
1
7.18
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Fracture
Fibrous, ConchoidalWalter Schumann
-
Cleavage
Distinct on {100}, poor on {110}; parting on {001}
Vitreous, pearly on cleavage
Mohs Hardness
7-8.53-4
2
10
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Chemical Composition
AlAl6O3BSi3O18
(Fe2+ ,Mg,Mn2+ ) 3(PO 4) 2 · 4H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references