Definition:
Dolomite (noun) is a type of limestone that consists of both calcium and magnesium. Chemically, it is written either as CaMg(Co3)2 or CaCO3.MgCO3. Dolomite is a natural ceramic material, so actual chemical composition can vary to a certain degree.
Dolomite is used as a high-temperature flux ( 2138 °F / 1170 °C) and can also act as a crystallization agent.
Examples:
Dolomite is used as a flux in many studio-made glazes.