Conchoidal, Conchoidal, Gemstones of the world (2001)
Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Metallic
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)
Mg 2Si 2O 6Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references