zinc ore - 20

Zinc (pronounced /ˈzɪŋk/ zingk, from German: Zink), also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2.

Detailed description:

Zinc is the 24th most abundant element in the Earth's crust and has five stable isotopes. The most exploited zinc ore is sphalerite, a zinc sulfide. The largest exploitable deposits are found in Australia, Canada, and the United States. Zinc production includes froth flotation of the ore, roasting, and final extraction using electricity (electrowinning).
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".
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Characteristics
Physical properties
Zinc, also referred to in nonscientific contexts as spelter, is a bluish-white, lustrous, diamagnetic metal, though most common commercial grades of the metal have a dull finish. It is somewhat less dense than iron and has a hexagonal crystal structure.
The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C. Above 210 °C, the metal becomes brittle again and can be pulverized by beating. Zinc is a fair conductor of electricity. For a metal, zinc has relatively low melting (420 °C) and boiling points (900 °C). Its melting point is the lowest of all the transition metals aside from mercury and cadmium.
Many alloys contain zinc, including brass, an alloy of zinc and copper. Other metals long known to form binary alloys with zinc are aluminium, antimony, bismuth, gold, iron, lead, mercury, silver, tin, magnesium, cobalt, nickel, tellurium and sodium. While neither zinc nor zirconium are ferromagnetic, their alloy ZrZn2 exhibits ferromagnetism below 35 K.
Occurrence
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.
Other minerals, from which zinc is extracted, include smithsonite (zinc carbonate), hemimorphite (zinc silicate), wurtzite (another zinc sulfide), and sometimes hydrozincite (basic zinc carbonate). With the exception of wurtzite, all these other minerals were formed as a result of weathering processes on the primordial zinc sulfides.
World zinc resources total about 1.8 gigatonnes. Nearly 200 megatonnes were economically viable in 2008; adding marginally economic and subeconomic reserves to that number, a total reserve base of 500 megatonnes has been identified. Large deposits are in Australia, Canada and the United States with the largest reserves in Iran. At the current rate of consumption, these reserves are estimated to be depleted sometime between 2027 and 2055. About 346 megatonnes have been extracted throughout history to 2002, and one estimate found that about 109 megatonnes of that remains in use.
Applications
The main end-uses for zinc are as follows:
1. Galvanizing: 59% - cars and construction
2. Diecasting: 16% - motor housings, door furniture, toys
3. Brass & Bronze: 10% - taps and pipes
4. Rolled zinc: 6.5% - roofing and guttering in some parts of Europe, coffins in southern Europe, and batteries
5. Chemicals: 6.0% - tyres and zinc cream
6. Miscellaneous: 2.5% - includes dust in batteries
Alloys
A widely used alloy which contains zinc is brass, in which copper is alloyed with anywhere from 3% to 45% zinc, depending upon the type of brass. Brass is generally more ductile and stronger than copper and has superior corrosion resistance. These properties make it useful in communication equipment, hardware, musical instruments, and water valves.

Other widely used alloys that contain zinc include nickel silver, typewriter metal, soft and aluminium solder, and commercial bronze. Zinc is also used in contemporary pipe organs as a substitute for the traditional lead/tin alloy in pipes.[102] Alloys of 85–88% zinc, 4–10% copper, and 2–8% aluminium find limited use in certain types of machine bearings. Zinc is the primary metal used in making American one cent coins since 1982.[103] The zinc core is coated with a thin layer of copper to give the impression of a copper coin. In 1994, 33,200 tonnes (36,600 short tons) of zinc were used to produce 13.6 billion pennies in the United States.[104]
Other industrial uses

Roughly one quarter of all zinc output, in the United States (2006), is consumed in the form of zinc compounds;[92] a variety of which are used industrially. Zinc oxide is widely used as a white pigment in paints, and as a catalyst in the manufacture of rubber.[10] It is also used as a heat disperser for the rubber and acts to protect its polymers from ultraviolet radiation (the same UV protection is conferred to plastics containing zinc oxide).[10] The semiconductor properties of zinc oxide make it useful in varistors and photocopying products.[111] The zinc zinc-oxide cycle is a two step thermochemical process based on zinc and zinc oxide for hydrogen production.[112]
Zinc chloride is often added to lumber as a fire retardant[113] and can be used as a wood preservative.[114] It is also used to make other chemicals.[113] Zinc methyl (Zn(CH3)2) is used in a number of organic syntheses.[115] Zinc sulfide (ZnS) is used in luminescent pigments such as on the hands of clocks, X-ray and television screens, and luminous paints.[116] Crystals of ZnS are used in lasers that operate in the mid-infrared part of the spectrum.[117] Zinc sulfate is a chemical in dyes and pigments.[113] Zinc pyrithione is used in antifouling paints.[118]
Zinc has been proposed as a salting material for nuclear weapons (cobalt is another, better-known salting material).[121] A jacket of isotopically enriched 64Zn, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 65Zn with a half-life of 244 days and produce massive gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several days.[121] Such a weapon is not known to have ever been built, tested, or used.[121] 65Zn is also used as a tracer to study how alloys that contain zinc wear out, or the path and the role of zinc in organisms.[122]
Medicine
Zinc is included in most single tablet over-the-counter daily vitamin and mineral supplements.[126] It is believed to possess antioxidant properties, which protect against premature aging of the skin and muscles of the body, although studies differ as to its effectiveness.[127] Zinc also helps speed up the healing process after an injury.[127]
The efficacy of zinc compounds when used to reduce the duration or severity of cold symptoms is controversial.[128] Zinc gluconate glycine and zinc acetate are used in throat lozenges or tablets to reduce the duration and the severity of cold symptoms.[129] Preparations include zinc oxide, zinc acetate, and zinc gluconate.[126]
See also: Alternative treatments used for the common cold#Zinc preparations


Zinc gluconate is one compound used for the delivery of zinc as a dietary supplement
Zinc preparations can protect against sunburn in the summer and windburn in the winter.[51] Applied thinly to a baby's diaper area (perineum) with each diaper change, it can protect against diaper rash.[51]