Handbook of mineralogy (2001)
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Na x[Fe2+2(Al,Fe3+ )]Al 6(BO 3) 3Si 6O 18(OH) 4Anthony et al , Handbook of mineralogy (2001)
Ca 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)