Platinum mainly occurs in Canada, in South Africa and in some countries of the former-USSR. From the Canadian deposits a mixture of ores is extracted that contain copper-nickel sulfides associated to volcanic rocks. Platinum and palladium can be found in this minerals in equal amounts while the presence of silver or gold is residual. The main deposits of South Africa are located in Merensky, northwest of Johannesburg. Here the platinum occurs in the order of 4 to 10 ppm, in rocks as piroxene, but always associated to iron, copper or nickel chromides and sulfides. In Russia there are wide deposits of this metal in minerals like peridotite, in the area of Noril'sk, Siberia. Can also be met considerable deposits of native platinum in the Ural Mountains. Although in smaller amounts, platinum is extracted in Colombia and in Alaska. The abundance of platinum in the earth crust is of the order of 0,01 gram per ton (i.e., about the double of that of gold).