Zinc is a metallic chemical element found in reasonable abundance around the world. It is classified in the transition metals, along with nickel and mercury, among others. The metal is used in a variety of alloys and compounds which have a range of uses, from sunscreen to fine art. Living organisms also rely on zinc as a valuable nutritional trace element; many foods are excellent sources of zinc, including seeds and whole grains.
Pure zinc is a bluish white, lustrous metal. It is extremely brittle at average room temperature, although when it is heated it becomes soft, malleable, and easily worked. When zinc is burned, it yields a bright blue to green flame, and the metal is reactive, combining readily with an assortment of other elements. On the periodic table of elements, zinc is identified with the symbol Zn, and the metal has an atomic number of 30.
Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC. Impure zinc metal was not produced in large scale until the 13th century in India, while the metal was unknown to Europe until the end of the 16th century. Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow".
Zinc makes up about 75 ppm (0.0075%) of the Earth's crust, making it the 24th most abundant element there. Soil contains 5–770 ppm of zinc with an average of 64 ppm. Seawater has only 30 ppb zinc and the atmosphere contains 0.1–4 µg/m3.
The element is normally found in association with other base metals such as copper and lead in ores. Zinc is a chalcophile , meaning the element has a low affinity for oxides and prefers to bond with sulfides. Chalcophiles formed as the crust solidified under the reducing conditions of the early Earth's atmosphere. Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinc-containing ore because its concentrate contains 60–62% zinc.
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