Brittle, Metallic, Brittle, Metallic
Conchoidal, Uneven, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal to uneven
Ca(Mg,Al)3(Al3Si)O10(OH)2
Ca 5(PO 4) 3(F,OH,Cl)Walter Schumann , Gemstones of the world (2001) More from other references