Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Mg 2Al 4Si 5O 18Ulrich Henn and Claudio C.
LiAl(PO 4)(OH,F)Walter Schumann , Gemstones of the world (2001) More from other references