Nickel does not occur as native metal. Its main minerals are the sulfides, the silicates and the arsenides. In the sulfides we stand out the pentlandite, the millerite, the polydymite and the siegenite, that can be found in Canada, ex-USSR, Cuba and U.S.A. The silicates garnierite and nickeliferrous limonite can be mainly found in Canada (Sudbury), ex-USSR, South Africa, Finland and USA (Minnesota). Among the arsenides we point out the niccolite, the gersdorffite, the chloanthite and the annabergite.