UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, UnevenArthur Thomas, Gemstones (2009), Brittle
Ca 2Mg 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.
MnPO 4Walter Schumann , Gemstones of the world (2001) More from other references