COPPER
Abundance and Extraction
Copper is the element with atomic number 29, symbolised as Cu. With its distinctive reddish hue, copper belongs to the transition metals family and specifically to the copper group, which it shares with gold and silver. Copper is relatively abundant in the Earth’s crust, with a concentration of 68 ppm (parts per million). For comparison, titanium has a concentration of 5650 ppm, while gold is much rarer at just 0.004 ppm. In 2023, the leading copper-producing countries were Chile, Peru, and the Democratic Republic of the Congo*.
Copper is one of the few metals that can be found in its native state. It is also commonly found in various mineral forms, particularly in sulfides, due to its chalcophile nature. The extraction of copper from ore involves several mechanical and physical processes, followed by refinement through electrolysis.
Properties
Mechanically, copper is both ductile and malleable. Its hardness and elasticity can be easily modified through cold working processes such as rolling or work hardening. Copper is the second most conductive metal after silver, both electrically and thermally. These mechanical and electrical properties make copper the metal of choice for manufacturing all types of electrical wires and cables. Copper does not oxidise when exposed to dry air but is reactive to water and carbon dioxide, leading to the formation of a protective layer of copper oxide, commonly known as verdigris, which provides excellent corrosion resistance.
Copper and gold are historically the first metals worked by humans. The earliest evidence of copper smelting dates back to 6000 BC. Its natural occurrence, ductility, malleability, and thermal conductivity quickly made it a valued metal in the manufacture of many useful objects, with its reddish colour giving it ornamental value.
Around 2700 BC, the Bronze Age began. Bronze, an alloy of copper and tin, is harder than copper and was initially used in the manufacture of sharp weapons. Copper thus marks the history of humanity. It has always been a prized metal for its properties in the production of many utilitarian, technical, scientific, and ornamental objects.
The exploitation of copper experienced renewed growth from the late 19th century with the advent of electricity and the industrial era.
Throughout history, copper, whether pure or alloyed, has always been present in clocks and watches.
Copper, whether in its pure state or as part of an alloy, is extensively utilised in horology. It plays a key role in the creation of movement components, cases, dials, tools, and even electrodes. In its unalloyed form, copper is particularly valued for its excellent electrical conductivity, making it ideal for contacts and conductors. Additionally, it serves as a carrier of abrasives in tribofinishing processes and is frequently chosen for the production of dial bases that are intended for enamelling.
As an alloy, copper is even more widespread. It is found in a blend with the brass and nickel silver used for plates, bridges, and wheels, as well as in many aluminium alloys (copper-aluminium) or beryllium alloys (copper-beryllium) intended for both movement and casing components. Highly valued by watchmakers for their extraordinary mechanical resistance, the use of copper-beryllium alloys is now strictly regulated and limited by the REACH regulation due to the toxicity of beryllium.