Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Conchoidal
Splintery
PbCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al 2SiO 5Michael OâDonoghue , Gems, Sixth Edition (2006)