Tenacity
-
-
Solubility
-
-
Durability
-
-
Specific Gravity
3.26-3.362.54-2.78
1
7.18
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Fracture
Conchoidal
Conchoidal
Cleavage
Good on {100}
Good in three directions
Mohs Hardness
6.5-75-6
2
10
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Chemical Composition
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references
K(Ca,Na) 2Si 4O 10(OH,F) · H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references