ConchoidalGemdat.org, Management Team (2012), ConchoidalGemdat.org, Management Team (2012)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Uneven
(Fe,Mg) 3Al 2(SiO 4) 3gemdat.org , Management Team (2012)
Mg 3Al 6(Si,Al,B) 5O 21(OH)Walter Schumann , Gemstones of the world (2001) More from other references