Uneven, Uneven, Gems, Sixth Edition (2006)
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Al 2O 3Michael OâDonoghue , Gems, Sixth Edition (2006)
Ca 9(Mg,Fe2+ )(PO 4) 6(PO 3OH)Anthony et al , Handbook of mineralogy (2001)