Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
(Ca,Mn2+ ,Fe2+ ) 3Al 2BSi 4O 15(OH)Anthony et al , Handbook of mineralogy (2001)
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.