Colorless, Greenish, Colorless, Green, gray, Yellow
Green, Yellow, Colorless, Grey, Brown, White, Red
Irregular/uneven, Uneven
Uneven, ConchoidalArthur Thomas, Brittle, Metallic
Ca 2Al 3(SiO 4) 3(OH)Walter Schumann , Gemstones of the world (2001) More from other references
Pb 5(PO 4) 3ClArthur Thomas , Gemstones (2009)