ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Perfect on {010}, good on {100}
Poor on {120}, in traces on {001}
Be 2BO 3(OH)Ulrich Henn and Claudio C.
TiO 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references