Two techniques that are used in metallurgy, which is concerned with extracting metals from ores, refining them, purifying them, and preparing them for practical applications.

While some metals; such as, gold and silver can be found uncombined with other elements in nature, most metals occur as minerals; that is, in chemical combination with nonmetallic elements.

When the combination is such that the extraction of a metal from a mineral is economically attractive, the combination is called an ore. The technique of producing metals from ore is called "process metallurgy" or "extraction metallurgy".