Sulfuric salts in water. They form what is known as non-carbonate hardness.

compounds containing sulfur and oxygen as SO4. Elevated sulfate levels are common in contaminated mine drainage. Sulfates can bond with hydrogen ions to form sulfuric acid, or bind to calcium atoms to form gypsum solid.

Inorganic salts of sulfuric acid (H2SO4) containing the divalent, negative ion .

Group of minerals that contains one or more metallic element in addition to the sulfate radical (SO4). All sulfates are transparent to translucent and soft. Most are heavy and lightly colored, and some are soluble in water. Rarer sulfates exist containing substitutions for the sulfate radical, such as the chromates, where it is replaced by a chromate radical (CrO4). The sulfates can be divided into the Hydrous sulfates and the Anhydrous sulfates. The chromates are usually classified as a sub-group of the sulfates.

A potentially corrosive, and naturally forming, substance found within certain soils. May cause concrete foundations to erode.