Uneven, Uneven, Gemstones of the world (2001) More from other references
ConchoidalGemdat.org, Management Team (2012), ConchoidalGemdat.org, Management Team (2012)
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references
(Fe,Mg) 3Al 2(SiO 4) 3gemdat.org , Management Team (2012)