ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Conchoidal, Metallic, UnevenArthur Thomas, Gemstones (2009), Brittle, Conchoidal
SiO 2Ulrich Henn and Claudio C.
Cu 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references