Conchoidal, Conchoidal, Gemstones of the world (2001)
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001) More from other references
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references