Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Subconchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Brittle
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references
(Ca,Ce)(Al,Ti,Mg)12O19