Hydrothermal Anhydrite in veins is usually hydrated to gypsum by groundwater in close to-floor exposures. It is usually connected to the minerals halite and sulfur. Gypsum is the commonest sulfate mineral.[17] Pure gypsum is white, but other substances found as impurities may give a variety of shades to regional deposits. https://www.propanraya.com/id/produk/eco-gypsum-ee-4050