Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
SiCArthur Thomas , Gemstones (2009)
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references