Hydrothermal anhydrite in veins is usually hydrated to gypsum by groundwater in near-floor exposures. It is usually related to the minerals halite and sulfur. Gypsum is the commonest sulfate mineral.[seventeen] Pure gypsum is white, but other substances observed as impurities may perhaps give a variety of colours to local deposits. https://www.propanraya.com/id/produk/eco-gypsum-ee-4050