Copper is one of the few metals that can occur in nature in a directly usable metallic form (called a native metal). This led to very early human use in several regions, from c. 8000 BC. Thousands of years later, it was the first metal to be smelted from sulfide ores, c. 5000 BC, the first metal to be cast into a shape in a mold c. 4000 BC, and the first metal to be purposefully alloyed with another metal, tin, to create bronze, c. 3500 BC.
The cultural role of copper has been important, particularly in currency. Romans in the 6th through 3rd centuries BC used copper lumps as money. At first, the copper itself was valued, but gradually the shape and look of the copper became more important. With an estimated annual output of around 15,000 t, Roman copper mining and smelting activities reached a scale unsurpassed until the time of the Industrial Revolution; the provinces most intensely mined were those of Hispania, Cyprus and in Central Europe.
Copper is one of a few metallic elements with a natural color other than gray or silver. Pure copper is orange-red and acquires a reddish tarnish when exposed to air. The characteristic color of copper results from the electronic transitions between the filled 3d and half-empty 4s atomic shells – the energy difference between these shells corresponds to orange light.
Because we don’t coat any of our pens, this material will patina and darken with time and use. Patina is a thin tarnish layer that forms on certain surfaces through oxidation or other chemical processes. It acts as a protective covering and also provides one of the coolest aspects of copper – it improves over time.