Copper is usually found in nature in association with sulfur. Pure copper metal is generally produced from a multistage process, beginning with the mining and concentrating of low-grade ores containing copper sulfide minerals, and followed by smelting and electrolytic refining to produce a pure copper cathode. Copper is one of the oldest metals ever used and has been one of the important materials in the development of civilization.
Because of its properties, singularly or in combination, of high ductility, malleability, and thermal and electrical conductivity, and its resistance to corrosion, copper has become a major industrial metal, ranking third after iron and aluminum in terms of quantities consumed. Electrical uses of copper, including power transmission and generation, building wiring, telecommunication, and electrical and electronic products, account for about three quarters of total copper use.
Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the form of magnetite (Fe3O4, 72.4% Fe), hematite (Fe
2O3, 69.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH)·n(H2O), 55% Fe) or siderite (FeCO3, 48.2% Fe).
Ores containing very high quantities of hematite or magnetite (greater than about 60% iron) are known as "natural ore" or "direct shipping ore", meaning they can be fed directly into iron-making blast furnaces. Iron ore is the raw material used to make pig iron, which is one of the main raw materials to make steel—98% of the mined iron ore is used to make steel.
Silver has been used for thousands of years as ornaments and utensils, for trade, and as the basis for many monetary systems. Of all the metals, pure silver has the whitest color, the highest optical reflectivity, and the highest thermal and electrical conductivity. Also, silver halides are photosensitive. Owing to the above properties, silver has many industrial applications such as in mirrors, electrical and electronic products, and photography, which is the largest single end use of silver. Silver's catalytic properties make it ideal for use as a catalyst in oxidation reactions; for example, the production of formaldehyde from methanol and air by means of silver screens or crystallites containing a minimum 99.95 weight-percent silver.
Aluminum is the second most abundant metallic element in the Earth's crust after silicon. It weighs about one-third as much as steel or copper; is malleable, ductile, and easily machined and cast; and has excellent corrosion resistance and durability.
Aluminum recovery from scrap (recycling) has become an important component of the aluminum industry. Sources for recycled aluminum include automobiles, windows and doors, appliances, and other products. However, it is the recycling of aluminum cans that seems to have the highest profile.
The metal gold, with atomic number 79 and the symbol ‘Au’, is one of the oldest metals used by humans. The aesthetic and physical properties have made it one of the most valuable metals in the world. The commodity gold is very malleable and ductile, resists corrosion or oxidation and is found almost always in a pure form. These properties ensured its application in many industries, but none so much as in jewelry. Between 50% and 60% of new gold is used for ornamental purposes, one third is used for investment purposes and the remainder in industries.
The largest deposits of gold can be found in South Africa, where around 60% of all new gold originates. Australia, the United States and Russia are other major producers. It is estimated that all the gold mined in all human history currently amounts to a cube of around 20 meters to a side in volume.