Tenacity
Solubility
Durability
Specific Gravity
Fracture
Cleavage
Mohs Hardness
Chemical Composition
Uneven, Irregular, Conchoidal
Na(Mg 3)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012)
Uneven, ConchoidalWalter Schumann, Conchoidal
None, may show partings on {0001} and {10 1 1}
Fe 2O 3Arthur Thomas , Gemstones (2009)