Dolomite

Dolomite (also known as dolostone, dolomite rock or dolomitic rock) is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg(CO3)2. In old USGS publications, it was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolomites or magnesium-rich limestones. Dolomite has a stoichiometric ratio of nearly equal amounts of magnesium and calcium. Most dolomites formed as a magnesium replacement of limestone or lime mud before lithification. Dolomite is resistant to erosion and can either contain bedded layers or be unbedded. It is less soluble than limestone in weakly acidic groundwater, but it can still develop solution features (karst) over time. Dolomite can act as an oil and natural gas reservoir.

The term dolostone was introduced in 1948 to avoid confusion with the mineral dolomite. The usage of the term dolostone is controversial because the name dolomite was first applied to the rock during the late 18th century and thus has technical precedence. The use of the term dolostone is not recommended by the Glossary of Geology published by the American Geological Institute. It is, however, used in some geological publications.

The geological process of conversion of calcite to dolomite is known as dolomitization and any intermediate product is known as "dolomitic limestone."

The "dolomite problem" refers to the vast worldwide depositions of dolomite in the past geologic record eluding a unified explanation for their formation.

The first geologist to distinguish dolomite rock from limestone was Belsazar Hacquet in 1778.