Conchoidal, Metallic, UnevenArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Cu 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al 2SiO 5Arthur Thomas , Gemstones (2009)