Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Al 2SiO 5Arthur Thomas , Gemstones (2009)
CaBe 2(PO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006)