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Cobalt is a
chemical element A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
with the symbol Co and atomic number 27. As with
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural
meteoric iron Meteoric iron, sometimes meteoritic iron, is a native metal and early-universe protoplanetary-disk remnant found in meteorites and made from the elements iron and nickel, mainly in the form of the mineral phases kamacite and taenite. Meteoric ir ...
. The free element, produced by reductive
smelting Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ...
, is a hard, lustrous, silver-gray
metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
. Cobalt-based blue pigments ( cobalt blue) have been used since ancient times for jewelry and paints, and to impart a distinctive blue tint to glass, but the color was for a long time thought to be due to the known metal
bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
. Miners had long used the name ''
kobold A kobold (occasionally cobold) is a mythical sprite. Having spread into Europe with various spellings including "goblin" and "hobgoblin", and later taking root and stemming from Germanic mythology, the concept survived into modern times in Ge ...
ore'' (German for ''goblin ore'') for some of the blue-pigment-producing
minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed ...
; they were so named because they were poor in known metals, and gave poisonous
arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...
-containing fumes when smelted. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the ''kobold''. Today, some cobalt is produced specifically from one of a number of metallic-lustered ores, such as
cobaltite Cobaltite is a sulfide mineral composed of cobalt, arsenic, and sulfur, Co As S. Its impurities may contain up to 10% iron and variable amounts of nickel.Klein, Cornelus and Cornrlius Hurlbut, 1996, ''Manual of Mineralogy'', 20th ed., Wiley, p. ...
(CoAsS). The element is, however, more usually produced as a by-product of
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
and
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
mining. The
Copperbelt The Copperbelt () is a natural region in Central Africa which sits on the border region between northern Zambia and the southern Democratic Republic of Congo. It is known for copper mining. Traditionally, the term ''Copperbelt'' includes the ...
in the
Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
(DRC) and
Zambia Zambia (), officially the Republic of Zambia, is a landlocked country at the crossroads of Central, Southern and East Africa, although it is typically referred to as being in Southern Africa at its most central point. Its neighbours are t ...
yields most of the global cobalt production. World production in 2016 was (according to
Natural Resources Canada Natural Resources Canada (NRCan; french: Ressources naturelles Canada; french: RNCan, label=none)Natural Resources Canada is the applied title under the Federal Identity Program; the legal title is Department of Natural Resources (). is the dep ...
), and the DRC alone accounted for more than 50%. Cobalt is primarily used in lithium-ion batteries, and in the manufacture of magnetic, wear-resistant and high-strength
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
s. The compounds cobalt silicate and cobalt(II) aluminate (CoAl2O4, cobalt blue) give a distinctive deep blue color to
glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
,
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
s,
ink Ink is a gel, sol, or solution that contains at least one colorant, such as a dye or pigment, and is used to color a surface to produce an image, text, or design. Ink is used for drawing or writing with a pen, brush, reed pen, or quill. Thicker ...
s, paints and varnishes. Cobalt occurs naturally as only one stable
isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
, cobalt-59.
Cobalt-60 Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2713 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisot ...
is a commercially important radioisotope, used as a
radioactive tracer A radioactive tracer, radiotracer, or radioactive label is a chemical compound in which one or more atoms have been replaced by a radionuclide so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by ...
and for the production of high-energy
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
s. Cobalt is the active center of a group of
coenzymes A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's role as a catalyst (a catalyst is a substance that increases the rate of a chemical reaction). Cofactors can be considered "helper molecules" that ass ...
called
cobalamin Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. ...
s.
Vitamin B B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. Though these vitamins share similar names (B1, B2, B3, etc.), they are chemically distinct compounds that often coex ...
, the best-known example of the type, is an essential
vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...
for all animals. Cobalt in inorganic form is also a micronutrient for
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
, algae, and
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
.


Characteristics

Cobalt is a ferromagnetic metal with a
specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...
of 8.9. The
Curie temperature In physics and materials science, the Curie temperature (''T''C), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism. The Cur ...
is and the magnetic moment is 1.6–1.7
Bohr magneton In atomic physics, the Bohr magneton (symbol ) is a physical constant and the natural unit for expressing the magnetic moment of an electron caused by its orbital or spin angular momentum. The Bohr magneton, in SI units is defined as \mu_\mat ...
s per
atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, ...
. Cobalt has a
relative permeability In multiphase flow in porous media, the relative permeability of a phase is a dimensionless measure of the effective permeability of that phase. It is the ratio of the effective permeability of that phase to the absolute permeability. It can be ...
two-thirds that of
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
.
Metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
lic cobalt occurs as two
crystallographic structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns t ...
s: hcp and
fcc The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
. The ideal transition temperature between the hcp and fcc structures is , but in practice the energy difference between them is so small that random intergrowth of the two is common. Cobalt is a weakly reducing metal that is protected from oxidation by a passivating oxide film. It is attacked by
halogens The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group i ...
and sulfur. Heating in
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
produces Co3O4 which loses oxygen at to give the monoxide CoO. The metal reacts with fluorine ( F2) at 520 K to give CoF3; with
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
( Cl2),
bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...
( Br2) and iodine ( I2), producing equivalent binary
halides In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
. It does not react with
hydrogen gas Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, a ...
( H2) or
nitrogen gas Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh ...
( N2) even when heated, but it does react with boron,
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
,
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
,
arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...
and sulfur. At ordinary temperatures, it reacts slowly with
mineral acids A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Ch ...
, and very slowly with moist, but not with dry, air.


Compounds

Common
oxidation states In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +5 are also known. A common oxidation state for simple compounds is +2 (cobalt(II)). These salts form the pink-colored
metal aquo complex In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorat ...
in water. Addition of chloride gives the intensely blue . In a borax bead
flame test A flame test is an analytical procedure used in chemistry to detect the presence of certain elements, primarily metal ions, based on each element's characteristic flame emission spectrum (which may be affected by the presence of chloride io ...
, cobalt shows deep blue in both oxidizing and reducing flames.


Oxygen and chalcogen compounds

Several oxides of cobalt are known. Green
cobalt(II) oxide Cobalt(II) oxide is an inorganic compound that has been described as an olive-green or gray solid. It is used extensively in the ceramics industry as an additive to create blue colored glazes and enamels as well as in the chemical industry for pr ...
(CoO) has rocksalt structure. It is readily oxidized with water and oxygen to brown cobalt(III) hydroxide (Co(OH)3). At temperatures of 600–700 °C, CoO oxidizes to the blue
cobalt(II,III) oxide Cobalt(II,III) oxide is an inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid. As a mixed valence compound, its formula is sometimes written as CoIICoIII2O4 and ...
(Co3O4), which has a spinel structure. Black
cobalt(III) oxide Cobalt(III) oxide is the inorganic compound with the formula of Co2O3. Although only two oxides of cobalt are well characterized, CoO and Co3O4, procedures claiming to give Co2O3 have been described. Thus treatment of Co(II) salts such as coba ...
(Co2O3) is also known. Cobalt oxides are
antiferromagnetic In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usually related to the spins of electrons, align in a regular pattern with neighboring spins (on different sublattices) pointing in opposite directions. ...
at low
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...
: CoO (
Néel temperature In physics and materials science, the Curie temperature (''T''C), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism. The Cur ...
291 K) and Co3O4 (Néel temperature: 40 K), which is analogous to
magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With th ...
(Fe3O4), with a mixture of +2 and +3 oxidation states. The principal
chalcogen The chalcogens (ore forming) ( ) are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioac ...
ides of cobalt include the black cobalt(II) sulfides, CoS2, which adopts a
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...
-like structure, and cobalt(III) sulfide (Co2S3).


Halides

Four
dihalide In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
s of cobalt(II) are known:
cobalt(II) fluoride Cobalt(II) fluoride is a chemical compound with the formula (CoF2). It is a pink crystalline solid compound which is antiferromagnetic at low temperatures (TN=37.7 K) The formula is given for both the red tetragonal crystal, (CoF2), and the tetra ...
(CoF2, pink),
cobalt(II) chloride Cobalt(II) chloride is an inorganic compound of cobalt and chlorine, with the formula . The compound forms several hydrates ·''n'', for ''n'' = 1, 2, 6, and 9. Claims of the formation of tri- and tetrahydrates have not been confirmed.M. T. Saug ...
(CoCl2, blue), cobalt(II) bromide (CoBr2, green), cobalt(II) iodide (CoI2, blue-black). These halides exist in anhydrous and hydrated forms. Whereas the anhydrous dichloride is blue, the hydrate is red. The reduction potential for the reaction + e → is +1.92 V, beyond that for
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
to chloride, +1.36 V. Consequently,
cobalt(III) chloride Cobalt(III) chloride or cobaltic chloride is an unstable and elusive compound of cobalt and chlorine with formula . In this compound, the cobalt atoms have a formal charge of +3.Arthur W. Chester, El-Ahmadi Heiba, Ralph M. Dessau, and William J. ...
would spontaneously reduce to cobalt(II) chloride and chlorine. Because the reduction potential for fluorine to fluoride is so high, +2.87 V,
cobalt(III) fluoride Cobalt(III) fluoride is the inorganic compound with the formula . Hydrates are also known. The anhydrous compound is a hygroscopic brown solid. It is used to synthesize organofluorine compounds. The related cobalt(III) chloride is also known but ...
is one of the few simple stable cobalt(III) compounds. Cobalt(III) fluoride, which is used in some fluorination reactions, reacts vigorously with water.


Coordination compounds

As for all metals, molecular compounds and polyatomic ions of cobalt are classified as
coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as '' ligands'' or complexing agents. ...
es, that is, molecules or ions that contain cobalt linked to one or more
ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elec ...
s. These can be combinations of a potentially infinite variety of molecules and ions, such as: *
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
, as in the cation hexaaquocobalt(II) . This pink-colored complex is the predominant cation in solid cobalt sulfate ·''x'', with ''x'' = 6 or 7, as well as in water solutions thereof. *
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
, as in ''cis''- diaquotetraamminecobalt(III) , in hexol , in (the anion of Erdmann's salt),Thomas P. McCutcheon and William J. Schuele (1953): "Complex Acids of Cobalt and Chromium. The Green Carbonatocobalt(III) Anion". ''Journal of the American Chemical Society'', volume 75, issue 8, pages 1845–1846. and in . *
carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate ...
, as in the green triscarbonatocobaltate(III) anion.H. F. Bauer and W. C. Drinkard (1960): "A General Synthesis of Cobalt(III) Complexes; A New Intermediate, Na3 o(CO3)33H2O". ''Journal of the American Chemical Society'', volume 82, issue 19, pages 5031–5032. .Fikru Tafesse, Elias Aphane, and Elizabeth Mongadi (2009): "Determination of the structural formula of sodium tris-carbonatocobaltate(III), Na3 o(CO3)33H2O by thermogravimetry". ''Journal of Thermal Analysis and Calorimetry'', volume 102, issue 1, pages 91–97. * nitrite as in . *
hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. I ...
, as in hexol. *
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride sa ...
, as in tetrachloridocobaltate(II) . *
bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochem ...
, as in . *
oxalate Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl ...
, as in trisoxalatocobaltate(III) . These attached groups affect the stability of
oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
s of the cobalt atoms, according to general principles of
electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the ...
and of the hardness–softness. For example, Co3+ complexes tend to have
ammine In coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia () ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelt with a single "m". Almost ...
ligands. Because phosphorus is softer than nitrogen, phosphine ligands tend to feature the softer Co2+ and Co+, an example being tris(triphenylphosphine)cobalt(I) chloride (). The more electronegative (and harder) oxide and fluoride can stabilize Co4+ and Co5+ derivatives, e.g. caesium hexafluorocobaltate(IV) (Cs2CoF6) and potassium
percobaltate Percobaltates are chemical compounds where the oxidation state of cobalt is +5. This is the highest established oxidation state of cobalt. The simplest of these are bi-metallic Group 1 oxides such as sodium percobaltate (Na3CoO4); which may be prod ...
(K3CoO4). Alfred Werner, a Nobel-prize winning pioneer in coordination chemistry, worked with compounds of
empirical formula In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, would simply be SO, as is the ...
. One of the isomers determined was
cobalt(III) hexammine chloride Hexaamminecobalt(III) chloride is the chemical compound with the formula o(NH3)6l3. It is the chloride salt of the coordination complex o(NH3)6sup>3+, which is considered an archetypal "Werner complex", named after the pioneer of coordination ...
. This coordination complex, a typical Werner-type complex, consists of a central cobalt atom coordinated by six
ammine In coordination chemistry, metal ammine complexes are metal complexes containing at least one ammonia () ligand. "Ammine" is spelled this way due to historical reasons; in contrast, alkyl or aryl bearing ligands are spelt with a single "m". Almost ...
orthogonal ligands and three
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride sa ...
counteranions. Using
chelating Chelation is a type of bonding of ions and molecules to metal ions. It involves the formation or presence of two or more separate coordinate bonds between a polydentate (multiple bonded) ligand and a single central metal atom. These ligands are ...
ethylenediamine ligands in place of ammonia gives tris(ethylenediamine)cobalt(III) (), which was one of the first
coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as '' ligands'' or complexing agents. ...
es to be resolved into optical isomers. The complex exists in the right- and left-handed forms of a "three-bladed propeller". This complex was first isolated by Werner as yellow-gold needle-like crystals.


Organometallic compounds

Cobaltocene Cobaltocene, known also as bis(cyclopentadienyl)cobalt(II) or even "bis Cp cobalt", is an organocobalt compound with the formula Co(C5H5)2. It is a dark purple solid that sublimes readily slightly above room temperature. Cobaltocene was discovere ...
is a
structural analog A structural analog (analogue in modern traditional English; Commonwealth English), also known as a chemical analog or simply an analog, is a compound having a structure similar to that of another compound, but differing from it in respect to a c ...
to ferrocene, with cobalt in place of iron. Cobaltocene is much more sensitive to
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
than ferrocene. Cobalt carbonyl ( Co2(CO)8) is a
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
in
carbonylation Carbonylation refers to reactions that introduce carbon monoxide into organic and inorganic substrates. Carbon monoxide is abundantly available and conveniently reactive, so it is widely used as a reactant in industrial chemistry. The term carbony ...
and
hydrosilylation Hydrosilylation, also called catalytic hydrosilation, describes the addition of Si-H bonds across unsaturated bonds."Hydrosilylation A Comprehensive Review on Recent Advances" B. Marciniec (ed.), Advances in Silicon Science, Springer Science, 2009 ...
reactions. Vitamin B12 (see below) is an organometallic compound found in nature and is the only
vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an essential micronutrient that an organism needs in small quantities for the proper functioning of its metabolism. Essential nutrie ...
that contains a metal atom. An example of an alkylcobalt complex in the otherwise uncommon +4 oxidation state of cobalt is the homoleptic complex tetrakis(1-norbornyl)cobalt(IV) (Co(1-norb)4), a transition metal-alkyl complex that is notable for its resistance to β-hydrogen elimination, in accord with
Bredt's rule Bredt's rule is an empirical observation in organic chemistry that states that a double bond cannot be placed at the bridgehead of a bridged ring system, unless the rings are large enough. The rule is named after Julius Bredt, who first discussed ...
. The cobalt(III) and cobalt(V) complexes and are also known.


Isotopes

59Co is the only stable cobalt
isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
and the only
isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
that exists naturally on Earth. Twenty-two
radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
s have been characterized: the most stable, 60Co, has a
half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
of 5.2714 years; 57Co has a half-life of 271.8 days; 56Co has a half-life of 77.27 days; and 58Co has a half-life of 70.86 days. All the other
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consi ...
isotopes of cobalt have half-lives shorter than 18 hours, and in most cases shorter than 1 second. This element also has 4
meta state A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ...
s, all of which have half-lives shorter than 15 minutes. The isotopes of cobalt range in
atomic weight Relative atomic mass (symbol: ''A''; sometimes abbreviated RAM or r.a.m.), also known by the deprecated synonym atomic weight, is a dimensionless physical quantity defined as the ratio of the average mass of atoms of a chemical element in a giv ...
from 50 u (50Co) to 73 u (73Co). The primary decay mode for isotopes with atomic mass unit values less than that of the only stable isotope, 59Co, is
electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...
and the primary mode of decay in isotopes with atomic mass greater than 59 atomic mass units is
beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
. The primary decay products below 59Co are element 26 (
iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
) isotopes; above that the decay products are element 28 (nickel) isotopes.


History

Cobalt compounds have been used for centuries to impart a rich blue color to
glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...
, glazes, and
ceramics A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
. Cobalt has been detected in Egyptian sculpture, Persian jewelry from the third millennium BC, in the ruins of Pompeii, destroyed in 79 AD, and in China, dating from the
Tang dynasty The Tang dynasty (, ; zh, t= ), or Tang Empire, was an imperial dynasty of China that ruled from 618 to 907 AD, with an interregnum between 690 and 705. It was preceded by the Sui dynasty and followed by the Five Dynasties and Ten Kingdom ...
(618–907 AD) and the
Ming dynasty The Ming dynasty (), officially the Great Ming, was an imperial dynasty of China, ruling from 1368 to 1644 following the collapse of the Mongol-led Yuan dynasty. The Ming dynasty was the last orthodox dynasty of China ruled by the Han peo ...
(1368–1644 AD). Cobalt has been used to color glass since the
Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second prin ...
. The excavation of the
Uluburun shipwreck The Uluburun Shipwreck is a Late Bronze Age shipwreck dated to the late 14th century BC, discovered close to the east shore of Uluburun (Grand Cape), Turkey, in the Mediterranean Sea. The shipwreck was discovered in the summer of 1982 by Mehmed ...
yielded an ingot of blue glass, cast during the 14th century BC. Blue glass from Egypt was either colored with copper, iron, or cobalt. The oldest cobalt-colored glass is from the eighteenth dynasty of Egypt (1550–1292 BC). The source for the cobalt the Egyptians used is not known. The word ''cobalt'' is derived from the German ', from ''
kobold A kobold (occasionally cobold) is a mythical sprite. Having spread into Europe with various spellings including "goblin" and "hobgoblin", and later taking root and stemming from Germanic mythology, the concept survived into modern times in Ge ...
'' meaning "goblin", a superstitious term used for the
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
of cobalt by miners. The first attempts to smelt those ores for copper or silver failed, yielding simply powder (cobalt(II) oxide) instead. Because the primary ores of cobalt always contain arsenic, smelting the ore oxidized the arsenic into the highly toxic and volatile
arsenic oxide Arsenic oxide may refer to any of the following: * Arsenic dioxide, As2O4 *Arsenic trioxide Arsenic trioxide, sold under the brand name Trisenox among others, is an inorganic compound and medication. As an industrial chemical, whose major uses ...
, adding to the notoriety of the ore. Swedish chemist
Georg Brandt Georg Brandt (26 June 1694 – 29 April 1768) was a Swedish chemist and mineralogist who discovered cobalt (c. 1735). He was the first person to discover a metal unknown in ancient times. He is also known for exposing fraudulent alchemists operatin ...
(1694–1768) is credited with discovering cobalt circa 1735, showing it to be a previously unknown element, distinct from bismuth and other traditional metals. Brandt called it a new "semi-metal". He showed that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the
bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period. All other known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers. During the 19th century, a significant part of the world's production of cobalt blue (a pigment made with cobalt compounds and alumina) and
smalt Cobalt glass—known as "smalt" when ground as a pigment—is a deep blue coloured glass prepared by including a cobalt compound, typically cobalt oxide or cobalt carbonate, in a glass melt. Cobalt is a very intense colouring agent and very litt ...
(
cobalt glass Cobalt glass—known as "smalt" when ground as a pigment—is a deep blue coloured glass prepared by including a cobalt compound, typically cobalt oxide or cobalt carbonate, in a glass melt. Cobalt is a very intense colouring agent and very litt ...
powdered for use for pigment purposes in ceramics and painting) was carried out at the Norwegian
Blaafarveværket Blaafarveværket, or the Blue Colour Works, was a mining and industrial company located at Åmot in Modum in Viken county, Norway, which existed from 1776 to 1898. The works mined cobalt ore and manufactured by smelting blue cobalt glass ( sma ...
. The first mines for the production of smalt in the 16th century were located in Norway, Sweden,
Saxony Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state of ...
and Hungary. With the discovery of cobalt ore in New Caledonia in 1864, the mining of cobalt in Europe declined. With the discovery of ore deposits in
Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central C ...
, Canada in 1904 and the discovery of even larger deposits in the Katanga Province in the Congo in 1914, the mining operations shifted again. When the Shaba conflict started in 1978, the copper mines of Katanga Province nearly stopped production. The impact on the world cobalt economy from this conflict was smaller than expected: cobalt is a rare metal, the pigment is highly toxic, and the industry had already established effective ways for recycling cobalt materials. In some cases, industry was able to change to cobalt-free alternatives. In 1938, John Livingood and
Glenn T. Seaborg Glenn Theodore Seaborg (; April 19, 1912February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work i ...
discovered the radioisotope
cobalt-60 Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2713 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisot ...
. This isotope was famously used at
Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...
in the 1950s to establish parity violation in radioactive
beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
. After World War II, the US wanted to guarantee the supply of cobalt ore for military uses (as the Germans had been doing) and prospected for cobalt within the U.S. border. An adequate supply of the ore was found in Idaho near Blackbird canyon in the side of a mountain. The firm Calera Mining Company started production at the site. It has been argued that cobalt will be one of the main objects of geopolitical competition in a world running on renewable energy and dependent on batteries, but this perspective has also been criticised for underestimating the power of economic incentives for expanded production.


Occurrence

The stable form of cobalt is produced in supernovae through the r-process. It comprises 0.0029% of the Earth's crust. Free cobalt (the native metal) is not found on Earth because of the oxygen in the atmosphere and the chlorine in the ocean. Both are abundant enough in the upper layers of the Earth's crust to prevent native metal cobalt from forming. Except as recently delivered in meteoric iron, pure cobalt in native metal form is unknown on Earth. The element has a medium abundance but natural compounds of cobalt are numerous and small amounts of cobalt compounds are found in most rocks, soils, plants, and animals. In nature, cobalt is frequently associated with
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
. Both are characteristic components of
meteoric iron Meteoric iron, sometimes meteoritic iron, is a native metal and early-universe protoplanetary-disk remnant found in meteorites and made from the elements iron and nickel, mainly in the form of the mineral phases kamacite and taenite. Meteoric ir ...
, though cobalt is much less abundant in iron meteorites than nickel. As with nickel, cobalt in meteoric iron
alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...
s may have been well enough protected from oxygen and moisture to remain as the free (but alloyed) metal, though neither element is seen in that form in the ancient terrestrial crust. Cobalt in compound form occurs in copper and nickel minerals. It is the major metallic component that combines with sulfur and arsenic in the sulfidic
cobaltite Cobaltite is a sulfide mineral composed of cobalt, arsenic, and sulfur, Co As S. Its impurities may contain up to 10% iron and variable amounts of nickel.Klein, Cornelus and Cornrlius Hurlbut, 1996, ''Manual of Mineralogy'', 20th ed., Wiley, p. ...
(CoAsS),
safflorite Safflorite is a rare cobalt iron arsenide mineral with the chemical formula . ''Pure'' safflorite is , but iron is virtually always present. Safflorite is a member of the three-way substitution series of arsenides known as the loellingite or loell ...
(CoAs2), glaucodot (), and
skutterudite Named after Skuterudåsen, a hill in Modum, Norway, skutterudite is a cobalt arsenide mineral containing variable amounts of nickel and iron substituting for cobalt with the ideal formula CoAs3. Some references give the arsenic a variable formula ...
(CoAs3) minerals. The mineral cattierite is similar to
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...
and occurs together with
vaesite Vaesite ( Ni S2) is a mineral found together with cattierite in the Democratic Republic of Congo. It is named after Johannes F. Vaes, a Belgian mineralologist. It is part of the pyrite group The pyrite group of minerals is a set of cubic crystal ...
in the copper deposits of Katanga Province. When it reaches the atmosphere,
weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
occurs; the sulfide minerals oxidize and form pink
erythrite Erythrite or red cobalt is a secondary hydrated cobalt arsenate mineral with the formula . Erythrite and annabergite, chemical formula , or nickel arsenate form a complete series with the general formula . Erythrite crystallizes in the monocli ...
("cobalt glance": Co3(AsO4)2·8H2O) and
spherocobaltite Spherocobaltite or sphaerocobaltite is a cobalt Carbonate minerals, carbonate mineral with chemical composition Cobalt(II) carbonate, CoCO3. In its (rare) pure form, it is typically a rose (color), rose-red color, but impure specimens can be shad ...
(CoCO3). Cobalt is also a constituent of
tobacco smoke Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C d ...
. The
tobacco plant ''Nicotiana'' () is a genus of herbaceous plants and shrubs in the family Solanaceae, that is indigenous to the Americas, Australia, Southwestern Africa and the South Pacific. Various ''Nicotiana'' species, commonly referred to as tobacco plants ...
readily absorbs and accumulates heavy metals like cobalt from the surrounding soil in its leaves. These are subsequently inhaled during
tobacco smoking Tobacco smoking is the practice of burning tobacco and ingesting the resulting smoke. The smoke may be inhaled, as is done with cigarettes, or simply released from the mouth, as is generally done with pipes and cigars. The practice is believed ...
.


In the ocean

Cobalt is a trace metal involved in photosynthesis and nitrogen fixation detected in most ocean basins and is a limiting micronutrient for phytoplankton and cyanobacteria. The Co-containing complex cobalamin is only synthesized by cyanobacteria and a few archaea, so dissolved cobalt concentrations are low in the upper ocean. Like Mn and Fe, Co has a hybrid profile of biological uptake by phytoplankton via photosynthesis in the upper ocean and scavenging in the deep ocean, although most scavenging is limited by complex organic ligands. Co is recycled in the ocean by decaying organic matter that sinks below the upper ocean, although most is scavenged by oxidizing bacteria. Sources of cobalt for many ocean bodies include rivers and terrestrial runoff with some input from hydrothermal vents. In the deep ocean, cobalt sources are found lying on top of seamounts (which can be large or small) where
ocean currents An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contour ...
sweep the ocean floor to clear
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...
over the span of millions of years allowing them to form as ferromanganese crusts. Although limited mapping of the seafloor has been done, preliminary investigation indicates that there is a large amount of these cobalt-rich crusts located in the Clarion Clipperton Zone, an area garnering increasing interest for
deep sea mining Deep sea mining is a growing subfield of experimental seabed mining that involves the retrieval of minerals and deposits from the ocean floor found at depths of or greater. As of 2021, the majority of marine mining efforts are limited to shal ...
ventures due to the mineral-rich environment within its domain. Anthropogenic input contributes as a non-natural source but in very low amounts. Dissolved cobalt (dCo) concentrations across oceans are controlled primarily by reservoirs where dissolved oxygen concentrations are low. The complex biochemical cycling of cobalt in the ocean is still not fully understood, but patterns of higher concentrations have been found in areas of low oxygen such as the Oxygen Minimum Zone (OMZ) in the Southern Atlantic Ocean. Cobalt is considered toxic for marine environments at high concentrations. Safe concentrations fall around 18 μg/L in marine waters for plankton such as diatoms.


Production

The main ores of cobalt are
cobaltite Cobaltite is a sulfide mineral composed of cobalt, arsenic, and sulfur, Co As S. Its impurities may contain up to 10% iron and variable amounts of nickel.Klein, Cornelus and Cornrlius Hurlbut, 1996, ''Manual of Mineralogy'', 20th ed., Wiley, p. ...
,
erythrite Erythrite or red cobalt is a secondary hydrated cobalt arsenate mineral with the formula . Erythrite and annabergite, chemical formula , or nickel arsenate form a complete series with the general formula . Erythrite crystallizes in the monocli ...
, glaucodot and
skutterudite Named after Skuterudåsen, a hill in Modum, Norway, skutterudite is a cobalt arsenide mineral containing variable amounts of nickel and iron substituting for cobalt with the ideal formula CoAs3. Some references give the arsenic a variable formula ...
(see above), but most cobalt is obtained by reducing the cobalt by-products of nickel and
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
mining and
smelting Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ...
. Since cobalt is generally produced as a by-product, the supply of cobalt depends to a great extent on the economic feasibility of copper and nickel mining in a given market. Demand for cobalt was projected to grow 6% in 2017. Primary cobalt deposits are rare, such as those occurring in hydrothermal deposits, associated with
ultramafic rock Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed ...
s, typified by the Bou-Azzer district of
Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria t ...
. At such locations, cobalt ores are mined exclusively, albeit at a lower concentration, and thus require more downstream processing for cobalt extraction. Several methods exist to separate cobalt from copper and nickel, depending on the concentration of cobalt and the exact composition of the used
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
. One method is
froth flotation Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, wher ...
, in which surfactants bind to ore components, leading to an enrichment of cobalt ores. Subsequent roasting converts the ores to cobalt sulfate, and the copper and the iron are oxidized to the oxide.
Leaching Leaching is the loss or extraction of certain materials from a carrier into a liquid (usually, but not always a solvent). and may refer to: * Leaching (agriculture), the loss of water-soluble plant nutrients from the soil; or applying a small amou ...
with water extracts the sulfate together with the
arsenate The arsenate ion is . An arsenate (compound) is any compound that contains this ion. Arsenates are salts or esters of arsenic acid. The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As(V). Arsenate res ...
s. The residues are further leached with sulfuric acid, yielding a solution of copper sulfate. Cobalt can also be leached from the slag of copper smelting. The products of the above-mentioned processes are transformed into the cobalt oxide (Co3O4). This oxide is reduced to metal by the
aluminothermic reaction Aluminothermic reactions are exothermic chemical reactions using aluminum as the reducing agent at high temperature. The process is industrially useful for production of alloys of iron. The most prominent example is the thermite reaction between ...
or reduction with carbon in a blast furnace.


Extraction

The
United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
estimates world reserves of cobalt at 7,100,000 metric tons. The
Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
(DRC) currently produces 63% of the world's cobalt. This market share may reach 73% by 2025 if planned expansions by mining producers like Glencore Plc take place as expected. But by 2030, global demand could be 47 times more than it was in 2017, Bloomberg New Energy Finance has estimated. Changes that Congo made to mining laws in 2002 attracted new investments in Congolese copper and cobalt projects. Glencore's Mutanda Mine shipped 24,500 tons of cobalt in 2016, 40% of Congo DRC's output and nearly a quarter of global production. After oversupply, Glencore closed Mutanda for two years in late 2019. Glencore's Katanga Mining project is resuming as well and should produce 300,000 tons of copper and 20,000 tons of cobalt by 2019, according to Glencore. After hitting near-decade highs in early 2018 above US$100,000 per tonne, prices for cobalt used in the global electric battery supply chain slipped by 45% in the following 2 years. With the upsurge in Electric (EV) vehicle demand in 2020 and early 2021, cobalt prices rose to US$54,000 per tonne by March 2021. Cobalt is ranked as a critical mineral by the United States, Japan, Republic of Korea, the United Kingdom and the European Union.


Democratic Republic of the Congo

In 2005, the top producer of cobalt was the copper deposits in the
Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
's Katanga Province. Formerly Shaba province, the area had almost 40% of global reserves, reported the British Geological Survey in 2009.
Artisanal mining An artisanal miner or small-scale miner (ASM) is a subsistence A subsistence economy is an economy directed to basic subsistence (the provision of food, clothing, shelter) rather than to the market. Henceforth, "subsistence" is understood as su ...
supplied 17% to 40% of the DRC production. Some 100,000 cobalt miners in Congo DRC use hand tools to dig hundreds of feet, with little planning and fewer safety measures, say workers and government and NGO officials, as well as ''
The Washington Post ''The Washington Post'' (also known as the ''Post'' and, informally, ''WaPo'') is an American daily newspaper published in Washington, D.C. It is the most widely circulated newspaper within the Washington metropolitan area and has a large nati ...
'' reporters' observations on visits to isolated mines. The lack of safety precautions frequently causes injuries or death. Mining pollutes the vicinity and exposes local wildlife and indigenous communities to toxic metals thought to cause birth defects and breathing difficulties, according to health officials. Human rights activists have alleged, and
investigative journalism Investigative journalism is a form of journalism in which reporters deeply investigate a single topic of interest, such as serious crimes, political corruption, or corporate wrongdoing. An investigative journalist may spend months or years res ...
reported confirmation, that
child labor Child labour refers to the exploitation of children through any form of work that deprives children of their childhood, interferes with their ability to attend regular school, and is mentally, physically, socially and morally harmful. Such e ...
is used in mining cobalt from African artisanal mines. This revelation prompted cell phone maker
Apple Inc. Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company ...
, on March 3, 2017, to stop buying ore from suppliers such as Zhejiang Huayou Cobalt who source from artisanal mines in the DRC, and begin using only suppliers that are verified to meet its workplace standards. There is a push globally by the EU and major car manufacturers (OEM) for global production of cobalt to be sourced and produced sustainably, responsibly and traceability of the supply chain. Mining companies are adopting and practising ESG initiatives in line with
OECD The Organisation for Economic Co-operation and Development (OECD; french: Organisation de coopération et de développement économiques, ''OCDE'') is an intergovernmental organisation with 38 member countries, founded in 1961 to stimulate e ...
Guidance and putting in place evidence of zero to low carbon footprint activities in the supply chain production of Lithium-ion batteries. These initiatives are already taking place with major mining companies, Artisanal and Small-Scale Mining companies (ASM). Car manufacturers and battery manufacturer supply chains Tesla, VW, BMW, BASF, Glencore are participating in several initiatives, such as the Responsible Cobalt Initiative and Cobalt for Development study. In 2018 BMW Group in partnership with BASF, Samsung SDI and Samsung Electronics have launched a pilot project in the DRC over one pilot mine, to improve conditions and address challenges for artisanal miners and the surrounding communities. The political and ethnic dynamics of the region have in the past caused outbreaks of violence and years of armed conflict and displaced populations. This instability affected the price of cobalt and also created perverse incentives for the combatants in the First and Second Congo Wars to prolong the fighting, since access to diamond mines and other valuable resources helped to finance their military goals—which frequently amounted to genocide—and also enriched the fighters themselves. While DR Congo has in the 2010s not recently been invaded by neighboring military forces, some of the richest mineral deposits adjoin areas where Tutsis and Hutus still frequently clash, unrest continues although on a smaller scale and refugees still flee outbreaks of violence. Cobalt extracted from small Congolese
artisanal mining An artisanal miner or small-scale miner (ASM) is a subsistence A subsistence economy is an economy directed to basic subsistence (the provision of food, clothing, shelter) rather than to the market. Henceforth, "subsistence" is understood as su ...
endeavors in 2007 supplied a single Chinese company, Congo DongFang International Mining. A subsidiary of Zhejiang Huayou Cobalt, one of the world's largest cobalt producers, Congo DongFang supplied cobalt to some of the world's largest battery manufacturers, who produced batteries for ubiquitous products like the Apple iPhones. Because of accused labour violations and environmental concerns,
LG Chem LG Chem Ltd. (Korean: LG화학), often referred to as LG Chemical, is the largest Korean chemical company and is headquartered in Seoul, South Korea. It was the 10th largest chemical company in the world by sales in 2017. It was first established ...
subsequently audited Congo DongFang in accordance with
OECD The Organisation for Economic Co-operation and Development (OECD; french: Organisation de coopération et de développement économiques, ''OCDE'') is an intergovernmental organisation with 38 member countries, founded in 1961 to stimulate e ...
guidelines. LG Chem, which also produces battery materials for car companies, imposed a code of conduct on all suppliers that it inspects. The Mukondo Mountain project, operated by the Central African Mining and Exploration Company (CAMEC) in Katanga Province, may be the richest cobalt reserve in the world. It produced an estimated one-third of the total global cobalt production in 2008. In July 2009, CAMEC announced a long-term agreement to deliver its entire annual
production Production may refer to: Economics and business * Production (economics) * Production, the act of manufacturing goods * Production, in the outline of industrial organization, the act of making products (goods and services) * Production as a stati ...
of cobalt concentrate from Mukondo Mountain to Zhejiang Galico Cobalt & Nickel Materials of China. In February 2018, global asset management firm
AllianceBernstein AllianceBernstein Holding L.P. (AB) is a global asset management firm providing investment management and research services worldwide to institutional, high-net-worth and retail investors. AllianceBernstein's headquarters are located in Nashvill ...
defined the DRC as economically "the
Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the fifth-largest country in Asia, the second-largest in the A ...
of the electric vehicle age", due to its cobalt resources, as essential to the lithium-ion batteries that drive electric vehicles. On March 9, 2018, President
Joseph Kabila Joseph Kabila Kabange ( , ; born 4 June 1971) is a Congolese politician who served as President of the Democratic Republic of the Congo between January 2001 and January 2019. He took office ten days after the assassination of his father, Pres ...
updated the 2002 mining code, increasing royalty charges and declaring cobalt and
coltan Coltan (short for columbite–tantalites and known industrially as tantalite) is a dull black metallic ore from which the elements niobium and tantalum are extracted. The niobium-dominant mineral in coltan is columbite (after niobium's original ...
"strategic metals". The 2002 mining code was effectively updated on December 4, 2018. In December 2019, International Rights Advocates, a human rights NGO, filed a landmark lawsuit against
Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...
, Tesla, Dell,
Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washin ...
and
Google Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
company
Alphabet An alphabet is a standardized set of basic written graphemes (called letters) that represent the phonemes of certain spoken languages. Not all writing systems represent language in this way; in a syllabary, each character represents a syllab ...
for "knowingly benefiting from and aiding and abetting the cruel and brutal use of young children" in mining cobalt. The companies in question denied their involvement in child labour.


Canada

In 2017, some exploration companies were planning to survey old silver and cobalt mines in the area of Cobalt, Ontario where significant deposits are believed to lie. Canada's
Sherritt International Sherritt International is a Canadian resource company, based in Toronto, Ontario. Sherritt is a world leader in the mining and refining of nickel and cobalt – metals essential for the growing adoption of electric vehicles. Its Technologies Grou ...
processes cobalt ores in nickel deposits from the Moa mines in
Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...
, and the island has several others mines in
Mayari In Kapampangan mythology, Mayari is the goddess of the moon and ruler of the world during nighttime. In Tagalog mythology According to Hiligaynon anthropologist F. Landa Jocano—in "Notes on Philippine Divinities" (1968)—the ancient Tagalo ...
, Camaguey, and
Pinar del Rio Pinar may refer to: * Pınar, Turkish feminine given name * Píñar, municipality located in the province of Granada, Spain * Pinar del Río, a city of Cuba * Pinar del Río Province, a province of Cuba * Pinar, Albania, village in Tirana County ...
. Continued investments by Sherritt International in Cuban nickel and cobalt production while acquiring mining rights for 17–20 years made the communist country third for cobalt reserves in 2019, before Canada itself.


Applications

In 2016, of cobalt was used. Cobalt has been used in the production of high-performance alloys. It is also used in some rechargeable batteries.


Alloys

Cobalt-based superalloys have historically consumed most of the cobalt produced. The temperature stability of these alloys makes them suitable for turbine blades for
gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
s and aircraft jet engines, although nickel-based
single-crystal In materials science, a single crystal (or single-crystal solid or monocrystalline solid) is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries In m ...
alloys surpass them in performance. Cobalt-based alloys are also
corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
- and wear-resistant, making them, like
titanium Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...
, useful for making orthopedic implants that don't wear down over time. The development of wear-resistant cobalt alloys started in the first decade of the 20th century with the stellite alloys, containing chromium with varying quantities of tungsten and carbon. Alloys with chromium and
tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
s are very hard and wear-resistant. Special cobalt-chromium- molybdenum alloys like Vitallium are used for
prosthetic In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...
parts (hip and knee replacements). Cobalt alloys are also used for dental prosthetics as a useful substitute for nickel, which may be allergenic. Some high-speed steels also contain cobalt for increased heat and wear resistance. The special alloys of aluminium, nickel, cobalt and iron, known as
Alnico Alnico is a family of iron alloys which in addition to iron are composed primarily of aluminium (Al), nickel (Ni), and cobalt (Co), hence the acronym ''al-ni-co''. They also include copper, and sometimes titanium. Alnico alloys are ferromagnetic, ...
, and of samarium and cobalt ( samarium-cobalt magnet) are used in
permanent magnets A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
. It is also alloyed with 95%
platinum Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver". Pla ...
for jewelry, yielding an alloy suitable for fine casting, which is also slightly magnetic.


Batteries

Lithium cobalt oxide Lithium cobalt oxide, sometimes called lithium cobaltateA. L. Emelina, M. A. Bykov, M. L. Kovba, B. M. Senyavin, E. V. Golubina (2011), "Thermochemical properties of lithium cobaltate". ''Russian Journal of Physical Chemistry'', volume 85, issue ...
(LiCoO2) is widely used in
lithium-ion battery A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also s ...
cathodes. The material is composed of cobalt oxide layers with the lithium intercalated. During discharge (''i.e.'' when not actively being charged), the lithium is released as lithium ions. Nickel-cadmium (NiCd) and
nickel metal hydride Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to r ...
(NiMH) batteries also include cobalt to improve the oxidation of nickel in the battery. Transparency Market Research estimated the global lithium-ion battery market at $30 billion in 2015 and predicted an increase to over US$75 billion by 2024. Although in 2018 most cobalt in batteries was used in a mobile device, a more recent application for cobalt is rechargeable batteries for electric cars. This industry has increased five-fold in its demand for cobalt, which makes it urgent to find new raw materials in more stable areas of the world. Demand is expected to continue or increase as the prevalence of electric vehicles increases. Exploration in 2016–2017 included the area around Cobalt, Ontario, an area where many silver mines ceased operation decades ago. Cobalt for electric vehicles increased 81% from the first half of 2018 to 7,200 tonnes in the first half of 2019, for a battery capacity of 46.3 GWh. The future of electric cars may depend on deep-sea mining, since cobalt is abundant in rocks on the seabed. Since child and slave labor have been repeatedly reported in cobalt mining, primarily in the artisanal mines of DR Congo, technology companies seeking an ethical supply chain have faced shortages of this raw material and the price of cobalt metal reached a nine-year high in October 2017, more than US$30 a pound, versus US$10 in late 2015. After oversupply, the price dropped to a more normal $15 in 2019. As a reaction to the issues with artisanal cobalt mining in DR Congo a number of cobalt suppliers and their customers have formed the ''Fair Cobalt Alliance'' (FCA) which aims to end the use of child labor and to improve the working conditions of cobalt mining and processing in the DR Congo. Members of FCA include Zhejiang Huayou Cobalt, Sono Motors, the ''Responsible Cobalt Initiative'',
Fairphone Fairphone is a Dutch electronics manufacturer that designs and produces smartphones with the goal of having a lower environmental footprint and better social impact than is common in the industry. In particular, the company aims to minimize the u ...
, Glencore and
Tesla, Inc. Tesla, Inc. ( or ) is an American multinational automotive and clean energy company headquartered in Austin, Texas. Tesla designs and manufactures electric vehicles (electric cars and trucks), battery energy storage from home to grid- ...
Research is being conducted by the European Union on the possibility to eliminate cobalt requirements in lithium-ion battery production. As of August 2020 battery makers have gradually reduced the cathode cobalt content from 1/3 ( NMC 111) to 2/10 (NMC 442) to currently 1/10 (NMC 811) and have also introduced the cobalt free LFP cathode into the battery packs of electric cars such as the
Tesla Model 3 The Tesla Model 3 is a compact executive sedan that is battery powered and produced by Tesla. Limited production of the Model 3 began in mid-2017, with the first production vehicle rolling off the assembly line on July 7, 2017. The offici ...
. In September 2020, Tesla outlined their plans to make their own, cobalt-free battery cells.


Catalysts

Several cobalt compounds are oxidation catalysts. Cobalt acetate is used to convert
xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are s ...
to terephthalic acid, the precursor of the bulk polymer polyethylene terephthalate. Typical catalysts are the cobalt
carboxylate In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an ion with negative charge. Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,...; ''carboxylat ...
s (known as cobalt soaps). They are also used in paints, varnishes, and inks as "drying agents" through the oxidation of
drying oils A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air, at room temperature. The oil hardens through a chemical reaction in which the components crosslink (and hence, polymerize) by the action of oxygen (not ...
. The same carboxylates are used to improve the adhesion between steel and rubber in steel-belted radial tires. In addition they are used as accelerators in
polyester resin Polyester resins are synthetic resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Maleic anhydride is a commonly used raw material with diacid functionality in unsaturated polyester resins. Unsaturated polyester res ...
systems. Cobalt-based catalysts are used in reactions involving
carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
. Cobalt is also a catalyst in the
Fischer–Tropsch process The Fischer–Tropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperatu ...
for the
hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organ ...
of carbon monoxide into liquid fuels.
Hydroformylation Hydroformylation, also known as oxo synthesis or oxo process, is an industrial process for the production of aldehydes from alkenes. This chemical reaction entails the net addition of a formyl group (CHO) and a hydrogen atom to a carbon-carbon d ...
of
alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...
s often uses cobalt octacarbonyl as a catalyst, The hydrodesulfurization of
petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
uses a catalyst derived from cobalt and molybdenum. This process helps to clean petroleum of sulfur impurities that interfere with the refining of liquid fuels.


Pigments and coloring

Before the 19th century, cobalt was predominantly used as a pigment. It has been used since the Middle Ages to make
smalt Cobalt glass—known as "smalt" when ground as a pigment—is a deep blue coloured glass prepared by including a cobalt compound, typically cobalt oxide or cobalt carbonate, in a glass melt. Cobalt is a very intense colouring agent and very litt ...
, a blue-colored glass. Smalt is produced by melting a mixture of roasted mineral smaltite,
quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
and
potassium carbonate Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and gl ...
, which yields a dark blue silicate glass, which is finely ground after the production. Smalt was widely used to color glass and as pigment for paintings. In 1780,
Sven Rinman Sven Rinman (23 June (N.S)/12 June (O.S) 1720 – 20 December 1792) was a Swedish chemist and mineralogist who discovered the pigment cobalt green Cobalt green is an ambiguous term for either of two families of green inorganic pigments. Bo ...
discovered cobalt green, and in 1802
Louis Jacques Thénard Louis Jacques Thénard (4 May 177721 June 1857) was a French chemist. Life He was born in a farm cottage near Nogent-sur-Seine in the Champagne district the son of a farm worker. In the post-Revolution French educational system , most boys rec ...
discovered cobalt blue. Cobalt pigments such as cobalt blue (cobalt aluminate),
cerulean Cerulean (), also spelled caerulean, is a shade of blue ranging between azure and a darker sky blue. The first recorded use of ''cerulean'' as a colour name in English was in 1590. The word is derived from the Latin word '' caeruleus'', "da ...
blue (cobalt(II) stannate), various hues of cobalt green (a mixture of
cobalt(II) oxide Cobalt(II) oxide is an inorganic compound that has been described as an olive-green or gray solid. It is used extensively in the ceramics industry as an additive to create blue colored glazes and enamels as well as in the chemical industry for pr ...
and
zinc oxide Zinc oxide is an inorganic compound with the formula . It is a white powder that is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cement ...
), and cobalt violet ( cobalt phosphate) are used as artist's pigments because of their superior chromatic stability.


Radioisotopes

Cobalt-60 Cobalt-60 (60Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2713 years. It is produced artificially in nuclear reactors. Deliberate industrial production depends on neutron activation of bulk samples of the monoisot ...
(Co-60 or 60Co) is useful as a gamma-ray source because it can be produced in predictable amounts with high activity by bombarding cobalt with
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
s. It produces
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
s with energies of 1.17 and 1.33 
MeV In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacu ...
. Cobalt is used in
external beam radiotherapy External beam radiotherapy (EBRT) is the most common form of radiotherapy (radiation therapy). The patient sits or lies on a couch and an external source of ionizing radiation is pointed at a particular part of the body. In contrast to brachyt ...
, sterilization of medical supplies and medical waste, radiation treatment of foods for sterilization (cold pasteurization),
industrial radiography Industrial radiography is a modality of non-destructive testing that uses ionizing radiation to inspect materials and components with the objective of locating and quantifying defects and degradation in material properties that would lead to the ...
(e.g. weld integrity radiographs), density measurements (e.g. concrete density measurements), and tank fill height switches. The metal has the unfortunate property of producing a fine dust, causing problems with
radiation protection Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Expos ...
. Cobalt from radiotherapy machines has been a serious hazard when not discarded properly, and one of the worst radiation contamination accidents in North America occurred in 1984, when a discarded radiotherapy unit containing cobalt-60 was mistakenly disassembled in a junkyard in Juarez, Mexico. Cobalt-60 has a radioactive half-life of 5.27 years. Loss of potency requires periodic replacement of the source in radiotherapy and is one reason why cobalt machines have been largely replaced by
linear accelerators A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear be ...
in modern radiation therapy.
Cobalt-57 Naturally occurring cobalt (Co) consists of a single stable isotope, Co. Twenty-eight radioisotopes have been characterized; the most stable are Co with a half-life of 5.2714 years, Co (271.8 days), Co (77.27 days), and Co (70.86 days). All othe ...
(Co-57 or 57Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for vitamin B uptake, and for the
Schilling test The Schilling test was a medical investigation used for patients with vitamin B (cobalamin) deficiency. The purpose of the test was to determine how well a patient is able to absorb B12 from their intestinal tract. The test is now considered obs ...
. Cobalt-57 is used as a source in
Mössbauer spectroscopy Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. This effect, discovered by Rudolf Mössbauer (sometimes written "Moessbauer", German: "Mößbauer") in 1958, consists of the nearly recoil-free emission and abs ...
and is one of several possible sources in
X-ray fluorescence X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis ...
devices.
Nuclear weapon design Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types: * pure fission weapons, the simplest and least technically ...
s could intentionally incorporate 59Co, some of which would be activated in a
nuclear explosion A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, tho ...
to produce 60Co. The 60Co, dispersed as
nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...
, is sometimes called a
cobalt bomb A cobalt bomb is a type of "salted bomb": a nuclear weapon designed to produce enhanced amounts of radioactive fallout, intended to contaminate a large area with radioactive material, potentially for the purpose of radiological warfare, mutual ...
.


Other uses

* Cobalt is used in electroplating for its attractive appearance, hardness, and resistance to
oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...
. * It is also used as a base primer coat for
porcelain Porcelain () is a ceramic material made by heating substances, generally including materials such as kaolinite, in a kiln to temperatures between . The strength and translucence of porcelain, relative to other types of pottery, arises main ...
enamels.


Biological role

Cobalt is essential to the metabolism of all
animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s. It is a key constituent of
cobalamin Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. ...
, also known as vitamin B, the primary biological reservoir of cobalt as an ultratrace element.
Bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
in the stomachs of
ruminant Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...
animals convert cobalt salts into vitamin B, a compound which can only be produced by bacteria or archaea. A minimal presence of cobalt in soils therefore markedly improves the health of
grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...
animals, and an uptake of 0.20 mg/kg a day is recommended because they have no other source of vitamin B. Proteins based on cobalamin use
corrin Corrin is a heterocyclic compound. It is the parent macrocycle related to the substituted derivative that is found in vitamin B12. Its name reflects that it is the "core" of vitamin B12 (cobalamins).Nelson, D. L.; Cox, M. M. "Lehninger, Princi ...
to hold the cobalt. Coenzyme B12 features a reactive C-Co bond that participates in the reactions. In humans, B12 has two types of
alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl is derived from a cycloa ...
ligand In coordination chemistry, a ligand is an ion or molecule ( functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elec ...
: methyl and adenosyl. MeB12 promotes methyl (−CH3) group transfers. The adenosyl version of B12 catalyzes rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent, X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine. Methylmalonyl coenzyme A mutase (MUT) converts MMl-CoA to Su-CoA, an important step in the extraction of energy from proteins and fats. Although far less common than other
metalloprotein Metalloprotein is a generic term for a protein that contains a metal ion cofactor. A large proportion of all proteins are part of this category. For instance, at least 1000 human proteins (out of ~20,000) contain zinc-binding protein domains al ...
s (e.g. those of zinc and iron), other cobaltoproteins are known besides B12. These proteins include methionine aminopeptidase 2, an enzyme that occurs in humans and other mammals that does not use the corrin ring of B12, but binds cobalt directly. Another non-corrin cobalt enzyme is nitrile hydratase, an enzyme in bacteria that metabolizes nitriles.


Cobalt deficiency

In humans, consumption of cobalt-containing vitamin B12 meets all needs for cobalt. For cattle and sheep, which meet vitamin B12 needs via synthesis by resident bacteria in the rumen, there is a function for inorganic cobalt. In the early 20th century, during the development of farming on the
North Island Volcanic Plateau The North Island Volcanic Plateau (often called the Central Plateau and occasionally the Waimarino Plateau) is a volcanic plateau covering much of central North Island of New Zealand with volcanoes, lava plateaus, and crater lakes. It contains ...
of New Zealand, cattle suffered from what was termed "bush sickness". It was discovered that the volcanic soils lacked the cobalt salts essential for the cattle food chain. The "coast disease" of sheep in the Ninety Mile Desert of the
Southeast The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each sepa ...
of
South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...
in the 1930s was found to originate in nutritional deficiencies of trace elements cobalt and copper. The cobalt deficiency was overcome by the development of "cobalt bullets", dense pellets of cobalt oxide mixed with clay given orally for lodging in the animal's
rumen The rumen, also known as a paunch, is the largest stomach compartment in ruminants and the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. The rumen's microbial favoring environment al ...
. File:Cobalamin.svg , alt=chemical diagram of cobalamin molecule,
Cobalamin Vitamin B12, also known as cobalamin, is a water-soluble vitamin involved in metabolism. It is one of eight B vitamins. It is required by animals, which use it as a cofactor in DNA synthesis, in both fatty acid and amino acid metabolism. ...
File:CSIRO ScienceImage 10487 Cobalt deficient sheep.jpg , alt=two cobalt-deficient sheep facing away from camera, Cobalt-deficient sheep


Health issues

The LD50 value for soluble cobalt salts has been estimated to be between 150 and 500 mg/kg.Donaldson, John D. and Beyersmann, Detmar (2005) "Cobalt and Cobalt Compounds" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. In the US, the
Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) has designated a
permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational ...
(PEL) in the workplace as a time-weighted average (TWA) of 0.1 mg/m3. The
National Institute for Occupational Safety and Health The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH) has set a
recommended exposure limit A recommended exposure limit (REL) is an occupational exposure limit that has been recommended by the United States National Institute for Occupational Safety and Health. The REL is a level that NIOSH believes would be protective of worker safet ...
(REL) of 0.05 mg/m3, time-weighted average. The
IDLH The term immediately dangerous to life or health (IDLH) is defined by the US National Institute for Occupational Safety and Health (NIOSH) as exposure to airborne contaminants that is "likely to cause death or immediate or delayed permanent advers ...
(immediately dangerous to life and health) value is 20 mg/m3. However, chronic cobalt ingestion has caused serious health problems at doses far less than the lethal dose. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led to a peculiar form of toxin-induced cardiomyopathy, which came to be known as ''beer drinker's cardiomyopathy''. Furthermore, cobalt metal is suspected of causing
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
(i.e., possibly
carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
ic, IARC Group 2B) as per the
International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and ...
(IARC) Monographs. It causes respiratory problems when inhaled. It also causes skin problems when touched; after
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...
and chromium, cobalt is a major cause of
contact dermatitis Contact dermatitis is a type of acute or chronic inflammation of the skin caused by exposure to chemical or physical agents. Symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, or swelling. These rashes are ...
.


References


Further reading

* * * * * * * * * *


External links


Cobalt
at ''
The Periodic Table of Videos ''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (University of Nottingham)
Centers for Disease and Prevention – Cobalt

The Cobalt Institute

Responsible Cobalt Institute
{{Good article Chemical elements Transition metals Dietary minerals Ferromagnetic materials IARC Group 2B carcinogens Child labour Cobalt mining Informal economy in Africa Resource economics Mining communities in Africa Extractive Industries Transparency Initiative Chemical elements with hexagonal close-packed structure Native element minerals