Nickel is a silver-white metal which occurs mainly in the sulfide and arsenic ores. It is extracted by roasting to NiO and then reducing using carbon. Pure nickel is manufactured by the Mond process, in which impure nickel is reacted with carbon monoxide (CO) to produce Ni(CO)4, which is then decomposed at 200C to yield 99.99% Ni. Nickel has an abundance of 80 ppm in the earth's crust.