Uneven, torn surfaces, (e.g. fractured metals)., Uneven, Gemstones (2009), torn surfaces, (e.g. fractured metals).
Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
FeO(OH)Arthur Thomas , Gemstones (2009)
SiO 2 · nH 2OGemdat.org , Management Team (2012)