Uneven, Uneven, Gemstones of the world (2001) More from other references
Uneven, Irregular, Management Team (2012)
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references
(Mg,Fe2+ ) 3Si 2O 5(OH) 4Anthony et al , Handbook of mineralogy (2001)