ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
PbCu(SO 4)(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)