An economically important source of nickel is the iron ore limonite, which often contains 1–2% nickel.
The element's name comes from a mischievous sprite of German miner mythology, Nickel (similar to Old Nick), who personified the fact that copper-nickel ores resisted refinement into copper. Nickel was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook the ore for a copper mineral, in the cobalt mines of Los, Hälsingland, Sweden. Use of nickel (as a natural meteoric nickel–iron alloy) has been traced as far back as 3500 BCE.
An iron–nickel mixture is thought to compose Earth's outer and inner cores. Meteoric nickel is found in combination with iron, a reflection of the origin of those elements as major end products of supernova nucleosynthesis. Even so, pure native nickel is found in Earth's crust only in tiny amounts, usually in ultramafic rocks, and in the interiors of larger nickel–iron meteorites that were not exposed to oxygen when outside Earth's atmosphere. Pure nickel, powdered to maximize the reactive surface area, shows a significant chemical activity, but larger pieces are slow to react with air under standard conditions because an oxide layer forms on the surface and prevents further corrosion (passivation). Nickel belongs to the transition metals and is hard and ductile. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a chemical element with the symbol Ni and atomic number 28. The triangles and squares identify the North-South polarity of one of their embedded magnets. Panel shapes include two types of interlocking triangles, interlockable squares, and circle or disks. The bars with magnets at each end are 27 mm (1.1 in) long, or 68 mm (2.7 in), or 53 mm (2.1 in) and flexible, or short rigid curves. The spheres are 0.588 in (14.9 mm) to 0.593 in (15.1 mm) in diameter (larger than Geomag), approximately 27.8 g (0.98 oz) in weight, and are prone to surface corrosion, unlike most other magnetic construction toys. Designed to be a cheaper version of the Geomag magnetic construction set, Magnetix's image suffered severely when an early manufacturing defect caused a death, and was subsequently sold under several different brands after the defect was corrected. Magnetix is a magnetic construction toy consisting of a combination of plastic building pieces containing embedded neodymium magnets, and steel bearing balls that can be connected to form geometric shapes and structures. Through biological evolution, sense organs and feeding structures also concentrate into the anterior region these collectively form the head. In bilaterally symmetrical animals, nervous tissues concentrate at the anterior region, forming structures responsible for information processing. Heads develop in animals by an evolutionary trend known as cephalization. Some very simple animals may not have a head, but many bilaterally symmetric forms do, regardless of size.
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