Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
Uneven, ConchoidalWalter Schumann
2,1 basal ; 2,1 prismatic ; 3,1 pinacoidal
Plagioclase Feldspar s: (Na,Ca)Al1-2Si3-2O8 Orthoclase Feldspar : KAlSi3O8
Subconchoidal, Conchoidal
(Fe,Mn)Ta 2O 6Walter Schumann , Gemstones of the world (2001) More from other references