Borax, also known as sodium tetraborate, is a compound. It is a white, crystalline solid that is composed of sodium, boron, oxygen, and hydrogen atoms. Borax is a natural mineral that is found in evaporite deposits. It is also produced commercially from other boron-containing minerals. Borax is used in a variety of applications, including as a flux in metallurgy, as a water softener, and as a preservative.