Uneven, Conchoidal, Brittle
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Uneven
(Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2
Mg 6Cr 2(CO 3)(OH) 16 · 4H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references