Hydrothermal Anhydrite in veins is often hydrated to gypsum by groundwater in near-surface area exposures. It is usually affiliated with the minerals halite and sulfur. Gypsum is the commonest sulfate mineral.[17] Pure gypsum is white, but other substances found as impurities could give a variety of hues to area deposits. https://www.propanraya.com/id/produk/eco-gypsum-ee-4050