Gemstones of the world (2001)
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
SiO 2Walter Schumann , Gemstones of the world (2001)
CaBe 2(PO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006)