ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Uneven
SiO 2Ulrich Henn and Claudio C.
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references