Uneven, ConchoidalArthur Thomas, Brittle, Metallic
Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Irregular
Pb 5(PO 4) 3ClArthur Thomas , Gemstones (2009)
SnO 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references