Metallurgy

Metallurgy deals with the study of metals and their ores as well as the processes for extracting, purifying, and alloying metals and production of metal objects. Humans have practiced the use of metals in various forms for nearly 9,000 years, beginning with copper during the eighth millennium BC. Cross-culturally, the processes involved with working metals are often shrouded with superstition and magical beliefs. Although the production of some metals requires sophisticated technology, there is virtually no culture in the world today that does not use at least some metal objects.

Common metals employed throughout the world include copper, silver, gold, lead, iron, tin, zinc, and arsenic. Of these, the first three occur in relatively pure or “native” form, whereas the others occur only in chemical compounds from which they must be extracted before use. Common metallic compounds from which metals are extracted include metallic salts, phosphates, and carbonates. Although some of these compounds exist in surface deposits, most metals and metal ores are mined.

The earliest documented uses of metals occurred in Iran and Anatolia during the eighth millennium BC in the Old World and circa 1500 BC in the Andes Mountains of the New World. In both cases, the first metals used were relatively pure forms of copper mined with stone and antler tools and processed with simple cold hammering techniques.

Later metal workers developed uses for alloys, that is, mixtures of a metal with one or more additional elements, often metals. Alloys are often favored because they offer technical properties that are not present in constituent elements. Common alloys include bronze (copper and either tin or arsenic), brass (copper and zinc), and pewter (tin, copper, antimony, and sometimes lead). Steel, one of the hardest metals, is made from alloying iron with carbon and sometimes other components such as manganese, chromium, and nickel.

The sōcalled “precious metals”—gold, silver, and platinum—are relatively rare and therefore expensive. Gold and silver especially have a long history of use as jewelry and other ornaments. Although they are obtainable in pure forms, they are often used as alloys to reduce the cost of objects and to create desirable characteristics of hardness and color.

Mines are usually used to extract metal ores from the earth if veins of ore are not available on the surface. However, native gold, called “placer gold,” occurs in alluvial deposits and can be collected by panning or washing. In most cultures, mining is considered a relatively undesirable job, even where the potential economic benefits are lucrative. This is due in part to the perceived, and often real, danger of underground mining. In addition to the apparent threats from explosives, heavy equipment, and possible cave-ins of mine shafts, miners face unseen dangers in the form of noxious gasses and airborne compounds, such as silica, that can damage the lungs.

Many cultures also maintain beliefs about supernatural beings that can influence the lives of miners. One such being is the Tio of Andean mines. Tio takes the form of a devil, often red with pointed horns, and inhabits a shrine located within the mine tunnels. Andean miners make offerings of cigarettes, coca leaves, and alcohol to propitiate Tio, who is asked to reciprocate in the form of pure ores of high value.

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