ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Uneven
Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Mg 3Al 6(Si,Al,B) 5O 21(OH)Walter Schumann , Gemstones of the world (2001) More from other references
Al2SiO4(F,OH)2