Common Uses for Magnesium Oxide

How Is Magnesium Oxide Made?

If you hear the words "magnesium oxide," they might not mean much to you. Yet this common mineral, found naturally in white powder form in metamorphic rocks, can be found in a surprising number of household and industrial items. The useful properties of this material make it an ideal tool for a wide range of activities.


Magnesium oxide in its hydrated form (magnesium hydroxide) is commonly used as an antacid. This works because magnesium oxide is a basic substance, meaning that it will neutralize acidity and end indigestion due to too much acid. Magnesium hydroxide is the active ingredient in such common over-the-counter remedies as milk of magnesia, Mylanta and Maalox.

Magnesium oxide also has short-term laxative effects and is prescribed for temporary relief from constipation.

Drying Agent

Magnesium oxide is a popular drying agent. In powder form, it is hygroscopic in nature, meaning that it attracts water molecules to itself from its surrounding environment. In doing this, the magnesium oxide will pull those molecules away from other things, keeping them dry.

Libraries and other large book and paper storage facilities will often use powdered magnesium oxide to help preserve paper. Rock climbers often use magnesium oxide as a way to reduce moisture from perspiration on their hands and handheld equipment, though other mineral powders are also used for this purpose.


Magnesium oxide is used as a refractory agent in the construction of crucibles. A crucible is a container which is intended to be placed in extremely high temperatures for the sake of heating its contents. Since the crucible itself must not be affected by the heat, it must be made with substances which retain their properties at high heat. Magnesium oxide is such a substance, so it is used in this manner.


Due to these same heat-resistant properties, magnesium oxide powder makes an excellent insulator. It is used as the mineral component of mineral-insulated copper-clad cables, a form of industrial cable used for the protection of particularly critical electrical circuits during a fire, including fire protection devices such as alarms or smoke control systems.

Dietary Supplement

Since it is a good source of magnesium, magnesium oxide is used as or in dietary supplements for humans and animals. In the case of animals, this is delivered as a food additive. For humans it can come in pill form or be included in multivitamins.

Other Uses

Magnesium oxide is often used in optical applications due to its refractive index (light-reflecting properties) in crystal form. Its basic properties are also utilized in the treatment of leather and its hygroscopic properties in the packaging of nuclear waste.