Dolomite is a calcium-magnesium carbonate flux used in the high fire range.
Dolomite supplies CaO and MgO.
Dolomite is calcium magnesium carbonate, theoretical formula CaMg(CO3)2. Pure dolomite, with exactly equal numbers of calcium and magnesium atoms, is formed by precipitation out of waters in which both are dissolved. Most dolomite, however, is formed when magnesium-rich waters seep through calcium carbonate rocks, and the magnesium ions replace some of the calcium (up to half). This process takes millions of years to complete, so some dolomite may have only incomplete replacement, and thus be higher in calcium than pure dolomite. Limestones in which dolomitization has occurred are known as dolomitic limestones or dolostones.
According to Obstler, dolomite may be substituted for whiting in many glazes without significant changes.
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