Bornite, also known as peacock ore, is a

sulfide mineral The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide () as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenide mineral, selenides, the tell ...

with

chemical composition A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds. Chemical formulas can be used to describe the relative amounts of elements present in a com ...

that crystallizes in the orthorhombic system (pseudo-cubic). It is an important copper ore.

Appearance

Bornite has a brown to copper-red color on fresh surfaces that tarnishes to various

iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstruc ...

shades of blue to purple in places. Its striking iridescence gives it the nickname ''peacock copper'' or ''peacock ore''.

Mineralogy

Bornite is an important copper ore mineral and occurs widely in

porphyry copper deposit Porphyry copper deposits are copper ore bodies that are formed from hydrothermal fluids that originate from a voluminous magma chamber several kilometers below the deposit itself. Predating or associated with those fluids are vertical dikes of ...

s along with the more common

chalcopyrite Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a Mohs scale, hardness of 3.5 to 4 ...

. Chalcopyrite and bornite are both typically replaced by chalcocite and covellite in the supergene enrichment zone of copper deposits. Bornite is also found as disseminations in

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

igneous rock Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial ...

s, in contact metamorphic

skarn Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, ...

deposits, in

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic c ...

s and in

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

cupriferous

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s. It is important as an

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...

for its

copper Copper is a chemical element; it has symbol Cu (from Latin ) 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 pinkish-orang ...

content of about 63 percent by mass.

Structure

At temperatures above , the structure is isometric with a unit cell that is about 5.50 Å on an edge. This structure is based on cubic close-packed

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

atoms, with copper and iron atoms randomly distributed into six of the eight

tetrahedral In geometry, a tetrahedron (: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular Face (geometry), faces, six straight Edge (geometry), edges, and four vertex (geometry), vertices. The tet ...

sites located in the octants of the cube. With cooling, the Fe and Cu become ordered, so that 5.5 Å subcells in which all eight tetrahedral sites are filled alternate with subcells in which only four of the tetrahedral sites are filled; symmetry is reduced to

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...

.Nesse, William D., "Sulfides and Related Minerals" in ''Introduction to Mineralogy,'' New York: Oxford University Press, 2000, p 429

Composition

Substantial variation in the relative amounts of copper and iron is possible and

solid solution A solid solution, a term popularly used for metals, is a homogeneous mixture of two compounds in solid state and having a single crystal structure. Many examples can be found in metallurgy, geology, and solid-state chemistry. The word "solutio ...

extends towards chalcopyrite (CuFeS₂) and digenite (Cu₉S₅). Exsolution of blebs and

lamellae Lamella (: lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal * Lame ...

of chalcopyrite, digenite, and chalcocite is common.

Form and twinning

Rare crystals are approximately cubic, dodecahedral, or

octahedral In geometry, an octahedron (: octahedra or octahedrons) is any polyhedron with eight faces. One special case is the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex. Many types of i ...

. Usually massive. Penetration twinning on the crystallographic direction, .

Occurrence

It occurs globally in copper ores with notable crystal localities in

Butte, Montana Butte ( ) is a consolidated city-county and the county seat of Silver Bow County, Montana, United States. In 1977, the city and county governments consolidated to form the sole entity of Butte-Silver Bow. The city covers , and, according to the 2 ...

and at

Bristol, Connecticut Bristol is a suburban city located in Hartford County, Connecticut, United States, southwest-west of Hartford, Connecticut, Hartford. The city is also 120 miles southwest from Boston, and approximately 100 miles northeast of New York City. The ...

in the U.S. It is also collected from the Carn Brea mine,

Illogan Illogan (pronounced ''il'luggan'', ) is a village and civil parish in west Cornwall, England, United Kingdom, two miles (3 km) northwest of Redruth. The population of Illogan was 5,404 at the 2011 census. In the same year the population of ...

, and elsewhere in

Cornwall Cornwall (; or ) is a Ceremonial counties of England, ceremonial county in South West England. It is also one of the Celtic nations and the homeland of the Cornish people. The county is bordered by the Atlantic Ocean to the north and west, ...

, England. Large crystals are found from the Frossnitz Alps, eastern Tirol, Austria; the Mangula mine, Lomagundi district, Zimbabwe; from the N'ouva mine, Talate, Morocco, the West Coast of Tasmania and in Dzhezkazgan, Kazakhstan. There are also traces of it found amongst the

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

in the

Pilbara The Pilbara () is a large, dry, sparsely populated regions of Western Australia, region in the north of Western Australia. It is known for its Indigenous Australians, Aboriginal people; wealth disparity; its ancient landscapes; the prevailing r ...

region of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

History and etymology

It was first described in 1725 for an occurrence in the

Ore Mountains The Ore Mountains (, or ; ) lie along the Czech–German border, separating the historical regions of Bohemia in the Czech Republic and Saxony in Germany. The highest peaks are the Klínovec in the Czech Republic (German: ''Keilberg'') at ab ...

Bohemia Bohemia ( ; ; ) is the westernmost and largest historical region of the Czech Republic. In a narrow, geographic sense, it roughly encompasses the territories of present-day Czechia that fall within the Elbe River's drainage basin, but historic ...

, in what is now the

Karlovy Vary Region The Karlovy Vary Region () is an administrative unit () of the Czech Republic, located in the westernmost part of the country. It is named after its capital Karlovy Vary. It is known for spas, which include Karlovy Vary and Mariánské Lázně. ...

of the Czech Republic. It was named in 1845 for Austrian mineralogist

Ignaz von Born Ignaz Edler von Born, also known as Ignatius von Born (, , ) (26 December 1742 in Alba Iulia, Grand Principality of Transylvania, Habsburg monarchy – 24 July 1791 in Vienna), was a mineralogist and metallurgist. He was a prominent freemason ...

References

Bibliography

* Palache, C., H. Berman, and C. Frondel (1944) ''Dana’s system of mineralogy'', (7th edition), v. I, 195–197.
Manning, P.G. (1966) ''A study of the bonding Properties of Sulphur in Bornite,'' The Canadian Mineralogist, 9, 85-94
{{ores Copper ores Iron minerals Sulfide minerals Orthorhombic minerals Minerals in space group 61