ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
SiO 2(+Al 2O 3)Walter Schumann , Gemstones of the world (2001)
MgF 2Ulrich Henn and Claudio C.