Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
Mg 3Al 6(Si,Al,B) 5O 21(OH)Walter Schumann , Gemstones of the world (2001) More from other references
Imperfect, poor one {100}
Zn 2(AsO 4)(OH) · H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references