Uneven, Uneven, Gems, Sixth Edition (2006)
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
From the Greek for oblique and fracture, descriptive of the cleavage
Perfect on [10 1 1] three directions with angle of 74° 55
(Na,K)AlSi 3O 8Michael OâDonoghue , Gems, Sixth Edition (2006)
CaCO 3Ulrich Henn and Claudio C.