Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
Al 2SiO 5Arthur Thomas , Gemstones (2009)
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references