Magnesite

Magnesite is not to be confused with Magnetite or Magnemite.

Magnesite is Ca)CO₃, is almost indistinguishable from magnesite.

Occurrence

Magnesite occurs as veins in and an alteration product of ultramafic rocks, chert.

Magnesite is also present within the regolith above ultramafic rocks as a secondary carbonate within soil and subsoil, where it is deposited as a consequence of dissolution of magnesium-bearing minerals by carbon dioxide within groundwaters.

Formation

Magnesite can be formed via greenschist facies;

Magnesite can also be formed via the carbonation of magnesian serpentine (lizardite) via the following reaction:
Serpentine + carbon dioxide → Talc + magnesite + Water

Fayalitic (iron-rich) olivine favors production of magnetite-magnesite-silica compositions.

Magnesite can also be formed from metasomatism in talc.

Uses

Magnesite can be used as a slag former in steelmaking furnaces, in conjunction with magnesium oxide lining. It can also be used as a catalyst and filler in the production of synthetic rubber and in the preparation of magnesium chemicals and fertilizers.

Similar to the production of lime, magnesite can be burned in the presence of charcoal to produce MgO, otherwise known as periclase. Such periclase is an important product in refractory materials.

References and external links

• Dana's Manual of Mineralogy ISBN 0-471-03288-3
• Smithsonian Rock and Gem ISBN 0-7566-0962-3
• Mineral Galleries
• Webmineral.com
• Mindat.org
• Minerals.net