ConchoidalGemdat.org, Management Team (2012), ConchoidalGemdat.org, Management Team (2012)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
(Fe,Mg) 3Al 2(SiO 4) 3gemdat.org , Management Team (2012)
Ca 2(Mg,Al) 6(Si,Al,B) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references