Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Irregular, Management Team (2012)
(Ca,Fe,Mn,Mg) 3Al 2BSi 4O 15(OH)Walter Schumann , Gemstones of the world (2001) More from other references
(Mg,Fe2+ ) 3Si 2O 5(OH) 4Anthony et al , Handbook of mineralogy (2001)