MgCO3

Magnesium carbonate, MgCO3, is an inorganic compound that occurs in nature as the mineral magnesite and can also be prepared synthetically. It is a white, odorless solid with low solubility in water and a tendency to decompose when heated.

In thermal processing, MgCO3 decomposes to magnesium oxide (MgO) and carbon dioxide (CO2) at elevated temperatures, typically above around 350 °C. At room temperature it remains relatively stable, though it is not highly soluble in water.

Industrial preparation commonly involves reacting magnesium oxide or magnesium hydroxide with carbon dioxide: MgO + CO2 → MgCO3 and Mg(OH)2 + CO2 → MgCO3 + H2O. It can also be formed by precipitation from aqueous magnesium salts under carbonate conditions.

Uses of magnesium carbonate are diverse. It is employed as a dietary supplement and antacid to supply magnesium ions. It serves as a food additive (anti-caking agent) and appears in cosmetics and pharmaceuticals. In sports and outdoor activities, it is used as chalk to improve grip in gymnastics and rock climbing. It also functions as a drying agent, filler or whitening agent in paints, plastics, and rubber, and as a polishing powder in some applications.

Occurrence and safety: natural magnesite deposits occur in sedimentary and metamorphic carbonate rocks and are mined for industrial use. Exposure to magnesium carbonate dust can irritate the eyes, nose, and throat; standard hygiene practices are recommended, and ingestion of large amounts should be avoided.