Basic Facts About Magnesium Oxide and Magnesium Hydroxide

The majority of magnesium oxide produced today is obtained from the processing of naturally occurring minerals such as magnesite (magnesium carbonate), magnesium chloride enriched brine, and seawater.

Large mineral deposits of magnesite are located in China, Austria, Brazil, Canada, the Commonwealth of Independent States (CIS), former Czechoslovakia, Greece, Turkey, North Korea, former Yugoslavia, and the United States.

In the production of magnesia products from naturally-mined sources, magnesium carbonate (magnesite) is heated from 700°C to 1000°C and thermally decomposes to produce magnesium oxide and carbon dioxide:

MgCO3 +   heat –>   MgO    +    CO2 (gas)

MgCO3 = magnesite
MgO = magnesium oxide
CO2 (gas) =  carbon dioxide

Magnesia products produced from naturally-mined sources typically have more impurities than magnesia produced from magnesium chloride enriched brine or seawater.

When water is added to magnesium oxide, magnesium oxide hydrates to an aqueous suspension of magnesium hydroxide:

MgO   +   H2O –>    Mg(OH)2

MgO = magnesium oxide
H2O = water
Mg(OH)2 = magnesium hydroxide

Physical properties for magnesium oxide and magnesium hydroxide include:

Magnesium Oxide and Magnesium Hydroxide Physical Properties
Chemical Name: Magnesium Oxide Magnesium Hydroxide
Chemical Formula: MgO Mg(OH)2
Physical State: solid solid
Molecular Weight: 40.31 g/mol 58.32 g/mol
Color: white white
Melting Point: 2827 +30ºC 350ºC
Density: 3.58 g/cm3 2.36 g/cm3

Next: Production of Magnesia