Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Uneven, Splintery, Brittle
None, may show partings on {0001} and {10 1 1}
Perfect on {110}, intersecting at 56° and 124°; partings on {100} and {010}