Here's the chemical reaction:

Mg + S → MgS

Magnesium sulfide is a white, crystalline solid that is used in various applications, including:

* Phosphor: It is used in fluorescent lamps and television screens as a phosphor.

* Fertilizer: It is sometimes used as a fertilizer to provide magnesium and sulfur to plants.

* Industrial uses: It is used in the production of other chemicals and in the manufacture of rubber and plastics.

It's important to note that this reaction requires high temperatures to occur.