Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Uneven, Gemstones of the world (2001) More from other references
(Mg,Fe2+ )Al 2O 4Gemdat.org , Management Team (2012) More from other references
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references