Handbook of mineralogy (2001)
Splintery, Granular, Splintery, Granular, Gemstones (2009)
(Ca,Mn2+ ) 2(SiO 3OH)(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