Copper

Copper is a reddish metal, atomic number 29, notable for being one of the very few metals that occurs in nature in a directly usable metallic form. That accident of chemistry is why it was worked long before smelting was understood: native copper could be hammered into shape by people with no metallurgy at all.

Its modern importance rests on a different property. Copper conducts electricity better than any metal except silver, and unlike silver it is abundant enough to wire a planet. Roughly two-thirds of copper production goes into electrical applications.

Copper conducts electricity well because of the electron it holds most loosely. A copper atom has a single electron outside a filled inner shell, and in the solid those electrons are not attached to particular atoms at all — they occupy states shared across the whole lattice and drift freely when a voltage is applied.

A metal conducts badly when something scatters those moving electrons: impurities, lattice defects, or the vibration of the atoms themselves. Copper is a soft, regular, close-packed lattice of a single element, which gives them comparatively little to collide with. That is also why conductivity falls as copper is warmed, and why alloying it — with zinc to make brass, or with nickel — reduces conductivity sharply while making the metal stronger. Silver is marginally better for the same reasons and costs a great deal more.

Most copper is now produced from sulfide ores, chiefly chalcopyrite, at grades well below one percent copper by mass. The ore is crushed, concentrated by froth flotation, then smelted and electrolytically refined to the 99.99% purity that electrical use demands.

The low grades are worth noting: a modern copper mine moves an enormous quantity of rock for each tonne of metal, which is why copper's environmental and energy footprint is dominated by extraction rather than by refining or fabrication.

Copper artefacts predate deliberate smelting by millennia. The decisive change came when it was found that adding tin produced bronze — harder, easier to cast, and capable of holding an edge. That discovery defines an archaeological age.

From Latin cuprum, itself a contraction of aes Cyprium, 'metal of Cyprus', after the island that supplied much of the Roman world's copper.

Electrical conduction dominates: copper carries the current in building wiring, motor windings, transformers and the grid itself, because only silver conducts better and silver is not affordable by the tonne. Electrification of transport and generation raises copper demand faster than almost any other metal.

Its other uses follow from corrosion resistance and workability — plumbing tube, roofing and cladding that weathers to a green patina, and heat exchangers. Alloyed, it becomes brass and bronze. Copper surfaces are also genuinely antimicrobial, which has revived interest in copper touch surfaces in hospitals.