ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
Mg 3(Al,Cr) 2(SiO 4) 3Gemdat.org , Management Team (2012)
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.