UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Ca 2B 5SiO 9(OH) 5Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
MgF 2Ulrich Henn and Claudio C.