Brittle, Metallic, Brittle, Metallic
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Be 4Si 2O 7(OH) 2Anthony et al , Handbook of mineralogy (2001)
SiO 2 + H 2OUlrich Henn and Claudio C.