Brittle, Metallic, Brittle, Metallic
Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Ca(Mg,Al)3(Al3Si)O10(OH)2
PbSO 4Michael OâDonoghue , Gems, Sixth edition (2006) More from other references