Zirconium is mainly used as a refractory and opacifier, although minor amounts are used as alloying agent for its strong resistance to corrosion. The great majority of zircon is used directly in a variety of high temperature applications. This material is refractory and hard, as well as resistant to chemical attack. A small fraction of the zircon is converted to the metal, which finds various niche applications. Because of zirconium's excellent resistance to corrosion, it is often used as an alloying agent in materials that are exposed to aggressive environments.