Why is dolomite calcined before magnesium is extracted from it?

In the context of magnesium processing, dolomite is calcined to convert it into magnesium oxide (MgO) and lime (CaO). This step is a necessary precursor to the thermal reduction process, where these oxides are reduced by silicon (Si) to extract magnesium.1

By calcining the dolomite, the material is prepared for a chemical reaction that yields magnesium gas and a slag of dicalcium silicate. Because this reduction reaction is endothermic—meaning it requires the input of heat to initiate and sustain—the conversion of dolomite into its oxide form is a critical stage in facilitating the subsequent extraction of the metal. This thermal reduction method, often referred to as the Pidgeon process, is a primary commercial technique for producing magnesium.12