Hydrothermal Anhydrite in veins is commonly hydrated to gypsum by groundwater in around-surface exposures. It is commonly related to the minerals halite and sulfur. Gypsum is the most common sulfate mineral.[17] Pure gypsum is white, but other substances identified as impurities could give an array of colours to area deposits. https://www.propanraya.com/id/produk/eco-gypsum-ee-4050