Pidgeon process
The Pidgeon process is one of the methods of magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 metal production, via a silicothermic reduction. Practical production requires roughly 35-40 MWh/ton of metal produced, which is on par with the molten salt electrolytic
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

 methods of production, though above the 7 MWh/ton theoretical minimum.
The basic chemical equations of this process are:
Si(s) + 2 MgO(s) ↔ SiO2(s) + 2 Mg(g) (high temperature, distillation boiling zone)
Mg(g) ↔ Mg(liq, s) (low temperature, distillation condensing zone)

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

 and magnesia react to produce silica and magnesium.

Though, according to Ellingham diagram
Ellingham diagram
An Ellingham diagram is a graph showing the temperature dependence of the stability for compounds. This analysis is usually used to evaluate the ease of reduction of metal oxides and sulphides. These diagrams were first constructed by Harold Ellingham in 1944...

s, this reaction is thermodynamically
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...

 unfavorable, in accordance with the Le Chatelier's principle
Le Châtelier's principle
In chemistry, Le Chatelier's principle, also called the Chatelier's principle, can be used to predict the effect of a change in conditions on a chemical equilibrium. The principle is named after Henry Louis Le Chatelier and sometimes Karl Ferdinand Braun who discovered it independently...

 of equilibriums, it can still be driven to the right by continuous supply of heat, and by removing one of the products, namely distilling out the magnesium vapor.