Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
Na 4(Al,Si) 12O 24Cl to Ca 4(Si,Al) 12O 24(CO 3,SO 4)Arthur Thomas , Gemstones (2009)
Uneven, Conchoidal, ConchoidalWalter Schumann
Indistinct on {001}; partings on {011} and {111}
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references