Uneven, Splintery, Conchoidal, Uneven, Splintery, Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001)
ConchoidalArthur Thomas, Gemstones (2009)
SiO 2Arthur Thomas , Gemstones (2009)
MnTa 2O 6Walter Schumann , Gemstones of the world (2001) More from other references