Ore, any naturally occuring material in the earth's crust containing one or more economically important minerals that can be profitably extracted. The most important ores are those containing metals. Usually, the desired metal is part of a chemical compound and must be separated from the other elements of the compound. When the metal in an ore is not chemically combined with other elements, it is called native metal. Gold, silver, copper, platinum, and several other metals are sometimes found as native metals. A complex ore is an ore from which two or more metals can be extracted. Lead-zinc ores, for example, are found in many parts of the world. Minerals of little or no value that occur in ores are called gangue.