Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, Brittle
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
(Mg,Fe2+ ) 2(Mg,Fe2+ ) 5Si 8O 22(OH) 2Anthony et al , Handbook of mineralogy (2001)
SiO 2Ulrich Henn and Claudio C.