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Dolomite

Dolomite is a mineral (formula CaMg(CO3)2) consisting of a calcium magnesium carbonate found in crystals and in beds as dolostone. A pure form of dolostone would be rare, however; it usually intergrades with limestone and is referred to as dolomitic limestone, or in old U. S. geologic literature as magnesian limestone.

Dolomite has physical properties similar to those of the mineral calcite, but is less soluble in hydrochloric acid.

There is uncertainty as to the cause of its formation, as vast deposits are present in ancient rock, but it is very rarely found being produced in modern environments. This is referred to as the “Dolomite Problem”. Dolomite accounts for about 10% of all sedimentary rock, including much that would have been produced near the surface of the Earth. However, experiments have only been able to synthesize dolomite under the high temperatures and pressures present in deeper layers.

One interesting reported case was the formation of dolomite in the kidneys of a dalmatian dog. This was believed to be due to chemical processes triggered by bacteria.

Recent research has found modern dolomite formation under anaerobic conditions in supersaturated saline lagoons along the Rio de Janeiro coast of Brazil, namely, Lagoa Vermelha and Brejo do Espinho. Similar processes have been discovered in the Coorong region of South Australia.

Dolomite is now thought to develop under these conditions only with the help of sulfate-reducing bacteria. The fact that conditions were better for the survival of these bacteria on the ancient Earth may explain the “Dolomite Problem”. This joins other research in pointing out many new interesting links between large-scale geology and small-scale microbiology (see geomicrobiology).

Dolomite is used as an ornamental stone and as a raw material for the manufacture of cement. It is also a source of magnesium oxide.

Dolomite


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