(e.g. graphite).
Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Fe 3(PO 4) 2 8H 2OUlrich Henn and Claudio C.
PbSO 4Michael OâDonoghue , Gems, Sixth edition (2006) More from other references