The mineral dolomite crystallizes in the trigonal-rhombohedral system. It forms white, tan, gray, or pink crystals. Dolomite is a double carbonate, having an alternating structural arrangement of calcium and magnesium ions. Unless it is in fine powder form, it does not rapidly dissolve or effervesce (fizz) in cold dilute hydrochloric acid as calcite does. Crystal twinning is common.
Because dolomite can be dissolved by slightly acidic water, areas where dolomite is an abundant rock-forming mineral are important as aquifers and contribute to karst terrain formation.
Dolomite is used for many of the same purposes as limestone, including as construction aggregate; in agriculture to neutralize soil acidity and supply calcium and magnesium; as a source of carbon dioxide; as dimension stone; as a filler in fertilizers and other products; as a flux in metallurgy; and in glass manufacturing. It cannot substitute for limestone in chemical processes that require a high-calcium limestone, such as manufacture of sodium carbonate. Dolomite is used for production of magnesium chemicals, such as Epsom salt, and is used as a magnesium supplement. It is also used in the manufacture of refractory materials.