Magnesite

Magnesite is a mineral with the chemical formula MgCO3 (magnesium carbonate). Similar to the production of lime, magnesite can be burned in the presence of charcoal to produce MgO, which, in the form of a mineral, is known as periclase. Large quantities of magnesite are burnt to make magnesium oxide: an important refractory (heat-resistant) material used as a lining in blast furnaces, kilns and incinerators.
Calcination temperatures determine the reactivity of resulting oxide products and the classifications of light burnt and dead burnt refer to the surface area and resulting reactivity of the product. ‘Light burnt’ product generally refers to calcination commencing at 450 °C and proceeding to an upper limit of 900 °C – which results in good surface area and reactivity.
Above 900 °C, the material loses its reactive crystalline structure and reverts to the chemically inert ‘dead-burnt’ product- which is preferred for use in refractory materials such as furnace linings.