UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Uneven, Uneven, Management Team (2012), Conchoidal, Brittle
Ca 2B 5SiO 9(OH) 5Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Fe 3O 4Ulrich Henn and Claudio C.