Magnesium carbonate is an inorganic compound with the chemical formula MgCO3, a molecular weight of 84.31, a relative density of approximately 3.037, and appears as a white granular powder.

Magnesium carbonate is slightly soluble in cold water, slowly dissolves in acids, decomposes at 350°C, and loses carbon dioxide at higher temperatures. Its trihydrate exists as colorless needle-like crystals, while the pentahydrate forms white monoclinic crystals. Magnesium carbonate can be prepared by passing carbon dioxide into an aqueous solution of magnesium salt and adding sodium carbonate. The anhydrous form can be obtained by drying the hydrate below 50°C.

Regarding whether magnesium carbonate is a precipitate, under normal circumstances, due to its slight solubility in water, it is generally considered a precipitate. However, there are exceptions; for instance, magnesium carbonate may hydrolyze in aqueous solutions to form the less soluble magnesium hydroxide precipitate, but this does not mean that all magnesium carbonate will immediately form a precipitate.

Magnesium carbonate has a wide range of applications, including the manufacture of magnesium salts, magnesium oxide, fire-resistant coatings, inks, glass, toothpaste, and rubber fillers. In the rubber industry, it is used as a reinforcing agent and filler; in the pharmaceutical field, magnesium carbonate serves as an antacid and laxative, showing significant effects in treating hyperacidity, gastric, and duodenal ulcers. Additionally, magnesium carbonate is involved in the production of glass products and the brightening treatment of enamel and ceramic surfaces.