Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Splintery, Granular, Splintery, Granular, Gemstones (2009)
(Ca,Mn2+ ,Fe2+ ) 3Al 2BSi 4O 15(OH)Anthony et al , Handbook of mineralogy (2001)
Ca 2(Mg,Fe) 5(OH) 2Walter Schumann , Gemstones of the world (2001) More from other references