Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
ConchoidalWalter Schumann
SiO 2Walter Schumann , Gemstones of the world (2001)
Perfect in one direction, indistinct in one direction
K2Na(Ca,Mn)2Ti[O|Si7O18(OH)]