Dolomite is a double carbonate rock with composition of Calcium & Magnesium occurring as arhombohedral crystals, proportion varying as per mining zone. Dolomite is harder and denser than the calcite form of calcium carbonate or limestone, and is more chemically inert and more impervious to acid attack. Chemically and structurally it is similar to calcite with half the calcium ions replaced by magnesium.

Dolomite is chiefly used as refractory, ramming, and fettling material in steel melting shop, and as fluxing material in blast furnace operation in secondary steel and ferromanganese manufacture. To a lesser extent it is used in the glass industry especially in sheet-glass manufacture. It also finds use in the manufacture of mineral wool.

In England, dolomite has become a useful source for the production of magnesite by reacting calcined dolomite with sea-water. The UK is meeting nearly 50% of her magnesite requirements by this method. Dolomite is also a good source of magnesium metal. The magnesium metal is extracted from dolomite by the well-known fero-silicon process.

Dolomite decomposes completely above 900ºC. The product resulting from this relatively low-temperature calcination is highly porous and reactive and is known as 'calcinated dolomite'. Dolomite is sometimes used both in the raw and calcined form as refractory material for hearth maintenance and for banking door in open hearth furnaces.

For most refractory uses, it is desirable to subject the dolomite to a heat treatment at a high temperature of the order of 1700ºC, to shrink the material thoroughly and render it less reactive. Dead burnt (D.B.) dolomite is sthe term generally used for the refractory made by firing dolomite, with or without additives, at high temperature to produce dense, well-shrunk particles.

In basic converters the bricks employed are generally of D.B. dolomite and sometimes also of D.B. magnesite. Dolomite bricks are kept in the outer lining because it has lower thermal conductivity than magnesite.