Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
UnevenWalter Schumann, Gemstones of the world (2001) More from other references, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Uneven
Al2SiO4(F,OH)2
(Zn,Fe)SMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references