Corporacin Nacional del Cobre de Chile (CODELCO) is the Chilean state owned copper mining company formed in 1976 from the foreign owned copper companies that were nationalised in 1971. It is currently the largest copper producing company in the world. It owns the world's largest known copper reserves and resources. CODELCO's principal product is cathode copper and is a large producer of rhenium, of which Chile is the world's largest producer. It also produces small amounts of gold and silver from refinery anode slimes, and the residue from electro refining of copper. The so-called CODELCO Law of April 1992 authorized CODELCO for the first time to form joint ventures with the private sector to work unexploited deposits. Thus, in a major step for CODELCO, in 1992, it invited domestic and foreign mining firms to participate in four joint explorations in northern Chile. Foreign owned private firms were to become increasingly important as new investment projects got underway.