Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Metallic
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
CaBSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al 2SiO 5Arthur Thomas , Gemstones (2009)