Niobium is a shiny, white, ductile metal. In air an oxide layer forms whose color depends on its thickness. Shades of blue, green and yellow are typical. Niobium’s chemical properties are very similar to those of tantalum. Niobium is one of the five major refractory metals (metals with very high resistance to heat and wear). Niobium is used with iron and other elements in stainless steel alloys and also in alloys with a variety of nonferrous metals, such as zirconium. Niobium alloys are strong and are often used in pipeline construction. The metal is used in superalloys for jet engines and heat resistant equipment. At cryogenic temperatures, niobium is a superconductor. Aerospace industry is the main application area of high purity niobium, mainly used for manufacturing engines and heat resistant components rockets and spacecraft. Niobium alloys have excellent thermal and thermal resistance and process-ability, which are widely used in aircraft components and gas turbine blades. In the United States, almost all jet fighter engines are made of niobium alloy.