-V- is a chemical element with atomic number 23. Vanadium is a soft, silvery gray, ductile transition metal. The formation of a greenish oxide layer stabilizes the metal. Vanadium is found only in chemically combined form in nature. Vanadium occurs naturally in about 65 different minerals and in fossil fuel deposits. Vanadium is produced in China and Russia from steel smelter slag; other countries produce it either from the flue dust of heavy oil, or as a byproduct of uranium mining. Vanadium is mainly used to produce specialty steel alloys such as high speed tool steels. The most important industrial vanadium compound, vanadium pentoxide, is used as a catalyst for the production of sulfuric acid.