ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.
(Zn,Mn2+ ,Fe2+ )(Fe3+ ,Mn3+ ) 2O 4Anthony et al , Handbook of mineralogy (2001)