Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references