SODIUM SULPHATE: ITS SOURCES AND USES USGS
Double sulphate of sodium and potassium, (Na,K)2S04. Composition, sodium sulphate (Na2S04), generally 21-38 per cent; potassium sulphate (K2S04), 62-78 per cent. Crystals hexagonal rhombohedral: Axial ratio c= 1,2839; (0001) A(10Tl) = 56° 0(T, (0001) A(1012) =36° 33'; common forms c (0001), m (10TO), e (10T2); habit rhombohedral, commonly thin tabular, also hi pseudohexagonal