Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
(Mg,Fe2+ )Al 2O 4Gemdat.org , Management Team (2012) More from other references
(Ca,Mn2+ ,Fe2+ ) 3Al 2BSi 4O 15(OH)Anthony et al , Handbook of mineralogy (2001)