ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, torn surfaces, (e.g. fractured metals)., Uneven, Gemstones (2009), torn surfaces, (e.g. fractured metals).
SiO 2Walter Schumann , Gemstones of the world (2001)
FeO(OH)Arthur Thomas , Gemstones (2009)