The mineral dolomite, commonly found in deposits of a sedimentary rock called dolostone, was named after the French mineralogist Deodat de Dolomieu. Basically, there are two types of materials referred to as dolomite: a true chemically uniform calcium magnesium carbonate with the chemical formula CaMg(CO3)2, and a dolomitic limestone – an irregular mixture of calcium and magnesium carbonates.
It is believed that dolomite was formed by replacement of some of the calcium in a calcium carbonate limestone deposit with magnesium while the sediment was undergoing lithification, being transformed from layers of dead clam and other sea animal shells into crystalized calcite or calcium carbonate. The resulting dolomite mineral, CaMg(CO3)2 is a real double salt.
In dolomite, the calcium and magnesium ions exist in separate layers in the crystal matrix, thus allowing several dolomite uses. The mineral has a calcium layer, then a magnesium layer, then a carbonate layer, and so on. Moreover, dolomite is both harder and denser than the calcite form of calcium carbonate or limestone, and is more chemically inert and more impervious to acid attack.
The several dolomite uses are driven by the inherent differences between dolomite and calcite. For instance, among the main dolomite uses, construction and building product applications are probably the most common, due to the mineral’s increased hardness and density, while asphalt and concrete applications prefer dolomite as a filler for its strength and hardness.
In addition, a number of applications exploit dolomite uses as a source of magnesium, for example glass and ceramics manufacture, a sintering agent in iron ore pelletization or as a flux agents in steel making. In agriculture, dolomite uses serve for pH control, while the chemical industry uses the mineral in making magnesium salts, including magnesia, magnesium oxide (MgO), which is used in pharmaceuticals.
As an industry mineral, however, dolomite uses are significantly fewer than calcite’s, mainly due to the relative lack of brightness deposits of dolomite. The alteration process through wich dolomite is formed generally brings in additional impurities that reduce its brightness or tint the stone brown or gray. However, in regions where high brightness dolomites can be found, dolomite uses share many of the calcium carbonate applications.
In the mineral’s typical form, however, dolomite uses are mostly as an ornamental stone, a concrete aggregate, or a source of magnesium oxide. Dolomite is a very important petroleum reservoir rock, and serves as the host rosk for large strata-bound Mississippi Valley-Type (MVT) ore deposits of base metals such as zinc, lead and copper. Also, in areas where calcite limestone is either uncommon or too expensive, dolomite uses serve as a replacement, allowing the mineral to act as a flux for the smelting of iron and steel. Meanwhile, large quantities of processed dolomite are used in the production of float glass. In horticulture, dolomitic limestone and dolomite are added to soils and soilless potting mixes to lower their acidity, as well as a magnesium source. For instance, dolomite uses are very common in home and container gardening.