Borax is a hydrated sodium tetraborate, Na2[B4O5(OH)4]·8H2O – the most common borate mineral. Borax may be colorless or white, transparent, or opaque. The anion is strongly hydrogen bonded to water. Borax is used as a source of boron compounds, and also to make heat-resistant glass, pottery glaze, water softeners in washing powders, fertilizers, and pharmaceuticals. It is found in large deposits in dried-up alkaline lakes in arid regions as crusts or masses of crystals. A major source is Searles Lake, California.