Nickel is a ductile metal, silver in color (for which reason it was mistaken, for a long time, for silver) and relatively hard. It has been used for millennia, but it was first isolated in mid-18th century and named for a German legendary mining character. It was initially isolated from cupronickel, but later other sources became known. It is often extracted from pyrrhotite or during the production of cobalt blue.
Nickel is useful because of its resistance to corrosion, and it is a good conductor of electricity and heat. It is malleable and reacts very slowly to exposure. It is ferromagnetic, meaning it reacts strongly to magnetization.
For a long time, humans were unable to extract nickel and merely used it incidentally or sporadically in plating and various alloys that were attractive because of their polished finish. Since the mid-19th century it has been commonly used in coins, and later acquired various other uses, in many cases in various alloys:
While nickel can be naturally found in water and soil, it is often encountered in areas with human pollution. In small quantities, it is eliminated through urine or the intestinal tract; in larger doses, however, it is toxic and may cause serious health conditions: