Rock Science

Malachite: The First Ore

- Steve Voynick

It is uncertain whether native gold or native copper was the first metal ever collected, but copper was clearly the utilitarian metal that led mankind out of the Stone Age. Native copper was less malleable, but harder, than gold, and simple hammering or casting could fashion it into various shapes for use as tools and weapons. But native copper alone was too rare to have a major societal impact.

Although copper is a relatively abundant metal, most is locked up in such minerals as chalcopyrite, cuprite and chalcocite, which are now the primary ores of copper. The term “ore” refers to any mineral containing a valuable constituent for which it is mined and worked. The valuable constituent in copper ores, of course, is copper, which is recovered in metallic form by the process of reduction smelting.

Smelting is not simply a matter of “melting” a metal out of its ore, but a complex, two-stage, thermo-chemical reaction. In the first stage, copper compounds are converted by thermal decomposition into copper oxide. In the second stage, a high-temperature, reduction reaction in the presence of a reducing agent such as carbon chemically reduces the copper oxide to metallic copper.