Uneven, Uneven, Gemstones of the world (2001) More from other references
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references
Mg 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)