Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references