UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
ConchoidalArthur Thomas, Gemstones (2009)
Ca 2Mg 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.
MnTa 2O 6Walter Schumann , Gemstones of the world (2001) More from other references