Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
SiCArthur Thomas , Gemstones (2009)
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.