Conchoidal, Brittle, Conchoidal
Uneven, torn surfaces, (e.g. fractured metals)., Uneven, Gemstones (2009), torn surfaces, (e.g. fractured metals).
AlO(OH)Walter Schumann , Gemstones of the world (2001) More from other references
FeO(OH)Arthur Thomas , Gemstones (2009)