Tenacity
Brittle
-
Solubility
-
-
Durability
-
-
Specific Gravity
1.793.1-3.2
1
7.18
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Fracture
Irregular/uneven
-
Cleavage
Perfect on {10bar10}
Vitreous, pearly on cleavage
Mohs Hardness
2.53-4
2
10
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Chemical Composition
Ca6(Al,Si)2(SO4)2B(OH)4(OH,O)12•26(H2O)
(Fe2+ ,Mg,Mn2+ ) 3(PO 4) 2 · 4H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references