Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Mg 2Al 4Si 5O 18Ulrich Henn and Claudio C.
CaBe 2(PO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006)