ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Be 2BO 3(OH)Ulrich Henn and Claudio C.
Ca 5(PO 4) 3FAnthony et al , Handbook of mineralogy (2001)