Uneven, Gemstones (2009), Splintery
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Ca 2NaHSi 3O 9Ulrich Henn and Claudio C.
SiO 2(+Al 2O 3)Walter Schumann , Gemstones of the world (2001)