Conchoidal, Brittle, Metallic, Conchoidal, Handbook of mineralogy (2001)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
(Mg,Fe2+ ) 3Si 2O 5(OH) 4Anthony et al , Handbook of mineralogy (2001)
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.