Irregular/uneven, Uneven
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Ca 2Al 3(SiO 4) 3(OH)Walter Schumann , Gemstones of the world (2001) More from other references
(Ca,Mn2+ ,Fe2+ ) 3Al 2BSi 4O 15(OH)Anthony et al , Handbook of mineralogy (2001)