Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Uneven, Irregular, Management Team (2012)
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references
(Mg,Fe2+ ) 3Si 2O 5(OH) 4Anthony et al , Handbook of mineralogy (2001)