Gems, Sixth Edition (2006)
Uneven, Sub-Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Quartz: SiO2 Rutile: TiO2
ZnCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references