Pentlandite is an

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

–

nickel Nickel is a chemical element; it has 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 slo ...

sulfide with the chemical formula . Pentlandite has a narrow variation range in nickel to iron ratios (Ni:Fe), but it is usually described as 1:1. In some cases, this ratio is skewed by the presence of

pyrrhotite Pyrrhotite (''Pyrrhus of Epirus, pyrrhos'' in Greek language, Greek meaning "flame-coloured"'')'' is an iron sulfide mineral with the formula Fe(1−x)S (x = 0 to 0.125). It is a nonstoichiometric compound, nonstoichiometric variant of FeS, th ...

inclusions. It also contains minor

cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, 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. ...

, usually at low levels as a fraction of weight. Pentlandite forms isometric crystals, but it is normally found in massive granular aggregates. It is brittle with a

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

of 3.5–4 and

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of 4.6–5.0 and is non-magnetic. It has a yellowish bronze color and a metallic luster. Pentlandite is found in abundance within

ultramafic 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 usua ...

rocks, making it one of the most important sources of mined nickel. It also occasionally occurs within mantle xenoliths and "black smoker" hydrothermal vents.

Etymology

It is named after Irish scientist Joseph Barclay Pentland (1797–1873), who first noted the mineral at Sudbury, Ontario. Canadian Copper Company Copper Cliff mine

Canadian Copper Company Copper Cliff mine

Identification

Physical and optical properties

In the field, pentlandite is often confused with other sulfide minerals, as they are all brassy yellowish in color and have a metallic luster. For this reason, the best way to discern pentlandite is by its paler color, lack of magnetism, and light brownish bronze streak. In contrast, pyrite,

and

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 ...

will all display much darker streaks: brownish black, greyish black, greenish black respectively. When looked at using reflected light ore microscopy, it possesses key diagnostic properties such as octahedral cleavage, and its alteration to bravoite, a pinkish to brownish violet sulfide mineral that occurs in euhedral to octahedral crystals. Pentlandite usually develops as granular inclusions within other sulfide minerals (mainly pyrrhotite), often taking the shape of thin veins or "flames". Although pentlandite is an opaque mineral, it exhibits a strong light creamy reflectance. PentlanditeTS

Mineral associations

Pentlandite occurs alongside

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 ...

s such as bravoite, chalcopyrite, cubanite, millerite, pyrrhotite, valleriite, as well as other minerals like

chromite Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of Iron, FeChromium, Cr2Oxygen, O4. It is an oxide mineral belonging to the spinel group. The ...

, ilmenite,

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

, and sperrylite. It is chemically similar to

mackinawite Mackinawite is an iron nickel sulfide mineral with the chemical formula (where x = 0 to 0.11). The mineral crystallizes in the tetragonal crystal system and has been described as a distorted, close packed, cubic array of S atoms with some of t ...

, godlevskite and horomanite. Pentlandite is synonymous with folgerite, horbachite, lillhammerite, and nicopyrite.

Pentlandite group

The pentlandite group is a subdivision of rare minerals that share similar chemical and structural properties with pentlandite, hence the name. Their chemical formula can be written as XY₈( S, Se)₈ in which X is usually replaced by

silver Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. ...

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

, and

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

, while

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 ...

takes the place of Y. Iron, nickel, and cobalt have the ability to occupy both X or Y positions. These minerals are: * Argentopentlandite Ag(Fe,Ni)₈S₈ * Cobalt pentlandite Co₉S₈ * Geffroyite (Ag,Cu,Fe)₉(Se,S)₈ * Manganese-shadlunite (Mn,Pb)(Cu,Fe)₈S₈ * Shadlunite (Pb,Cd)(Fe,Cu)₈S₈ * Oberthürite Rh₃Ni₃₂S₃₂ * Sugakiite Cu(Fe,Ni)₈S₈

Paragenesis

Pentlandite is the most common terrestrial nickel sulfide. It typically forms during cooling of a sulfide melt. These sulfide melts, in turn, are typically formed during the evolution of a silicate melt. Because nickel is a chalcophile element, it has preference for (i.e. it "partitions into") sulfide phases. In sulfide undersaturated melts, nickel substitutes for other

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinid ...

s within ferromagnesian minerals, the most common being

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

, as well as nickeliferous varieties of amphibole, biotite, pyroxene and spinel. Nickel substitutes most readily for Fe²⁺ and Co²⁺ because or their similarity in size and charge. In sulfide saturated melts, nickel behaves as a chalcophile element and partitions strongly into the sulfide phase. Because most nickel behaves as a compatible element in igneous differentiation processes, the formation of nickel-bearing sulfides is essentially restricted to sulfide saturated mafic and ultramafic melts. Minor amounts of nickel sulfides are found in mantle

peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high pr ...

s. The behaviour of sulfide melts is complex and is affected by copper, nickel, iron, and sulfur ratios. Typically, above 1100 °C, only one sulfide melt exists. Upon cooling to 1000 °C, a solid containing mostly Fe and minor amounts of Ni and Cu is formed. This phase is called monosulfide solid solution (MSS), and is unstable at low temperatures decomposing to mixtures of pentlandite and

, and (rarely) pyrite. It is only upon cooling past ~ (dependent on composition) that the MSS undergoes exsolution. A separate phase, usually a copper-rich sulfide liquid may also form, giving rise to

upon cooling. These phases typically form

aphanitic Aphanites (adj. ''aphanitic''; ) are igneous rocks that are so fine-grained that their component mineral crystals are not visible to the naked eye (in contrast to phanerites, in which the crystals are visible to the unaided eye). This geo ...

equigranular massive sulfides, or are present as disseminated sulfides within rocks composed mostly of silicates. Pristine magmatic massive sulfide are rarely preserved as most deposits of nickeliferous sulfide have been metamorphosed. Metamorphism at a grade equal to, or higher than,

greenschist Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as Chlorite ...

facies will cause solid massive sulfides to deform in a ductile fashion and to travel some distance into the country rock and along structures. Upon cessation of metamorphism, the sulfides may inherit a foliated or sheared texture, and typically develop bright, equigranular to globular aggregates of porphyroblastic pentlandite crystals known colloquially as "fish scales". Metamorphism may also alter the concentration of nickel and the Ni:Fe ratio and Ni:S ratio of the sulfides. In this case, pentlandite may be replaced by millerite, and rarely heazlewoodite. Metamorphism may also be associated with metasomatism, and it is particularly common for

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

to react with pre-existing sulfides, producing nickeline, gersdorffite and other Ni–Co arsenides.

Occurrence

Pentlandite is found within the lower margins of mineralized

layered intrusion A layered intrusion is a large sill-like body of igneous rock which exhibits vertical layering or differences in composition and texture. These intrusions can be many kilometres in area covering from around to over and several hundred metres t ...

s, the best examples being the Bushveld igneous complex,

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

, the Voisey's Bay troctolite intrusive complex in

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, the Duluth gabbro, in North America, and various other localities throughout the world. In these locations, pentlandite is considered an important nickel ore. Pentlandite is also the dominant ore mineral occurring in Kambalda type komatiitic nickel ore deposits, the prime example of which can be found in the Yilgarn craton 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 ...

. Similar deposits exist at Nkomati,

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

, in the Thompson Belt, Canada, and a few examples from Brazil. Pentlandite, but primarily chalcopyrite and PGEs, are also obtained from the supergiant

Norilsk Norilsk ( rus, Нори́льск, p=nɐˈrʲilʲsk) is a closed city in Krasnoyarsk Krai, Russia, located south of the western Taymyr Peninsula, around 90 km east of the Yenisei, Yenisey River and 1,500 km north of Krasnoyarsk. Norilsk is 300 ...

nickel deposit, in trans-Siberian Russia. The

Sudbury Basin The Sudbury Basin (), also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geology, geological structure in Ontario, Canada. It is among the oldest- and largest-known List of impact structures on Earth, impact structures ...

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

, Canada, is associated with a large

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

impact crater. The pentlandite-chalcopyrite-pyrrhotite ore around the Sudbury Structure formed from sulfide melts that segregated from the melt sheet produced by the impact.

Gallery

File:Pentlandite, Sudbury, Ontario, Canada-8779.jpg, Pentlandite specimen from Sudbury,

File:Pentlandite - Kambalda, Coolgardie Shire, Western Australia.jpg, Pentlandite specimen from Kambalda, Western Australia File:Pyrrhotite-pentlandite-chalcopyrite-magnetite (Worthington, Sudbury Impact Structure, Ontario, Canada) 2 (18887348131).jpg, Pentlandite occurring with

, and

. Specimen from Sudbury,

File:Pentlandite-Chalcopyrite-Pyrrhotite-199634.jpg, Pentlandite occurring with

and

. Specimen from Sudbury,

File:Pentlandite in pyrrhotite, South Mine, Sudbury, Ontario.jpg, Pentlandite occurring with

and

. Specimen from Sudbury,

File:Pyrrhotite-pentlandite-chalcopyrite (Gap Nickel Mine, Lancaster County, Pennsylvania, USA).jpg, Pentlandite occurring with

and

. Specimen from Gap Nickel Mine,

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

, USA File:Pentlandite (47753091111).jpg, Pentlandite from Rankin Inlet Nickel Mine,

Nunavut Nunavut is the largest and northernmost Provinces and territories of Canada#Territories, territory of Canada. It was separated officially from the Northwest Territories on April 1, 1999, via the ''Nunavut Act'' and the Nunavut Land Claims Agr ...

File:Pentlandite (47700373212).jpg, Pentlandite from Sudbury,

File:Pentlandite with Magnetite and Heazlewoodite (46836617345).jpg, Pentlandite occurring with heazlewoodite and magnetite. Specimen from

Trial Harbour Trial Harbour is a rural locality in the local government area (LGA) of West Coast Council, West Coast in the North-west and west LGA Region, North-west and west LGA region of Tasmania. The locality is about south-west of the town of Zeehan, Tas ...

Zeehan Zeehan is a town on the west coast of Tasmania, Australia south-west of Burnie. It is part of the West Coast Council, along with the seaport Strahan and neighbouring mining towns of Rosebery and Queenstown. History The greater Zeehan a ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

File:Pentlandite with Chalcopyrite and Magnetite (47700373052).jpg, Pentlandite occurring with

and

. Specimen from Sudbury

File:Pentlandite with Pyrrhotite (47700373172).jpg, Pentlandite occurring with

. Specimen from Worthington,

File:Pentlandite with Chalcopyrite (48603535937).jpg, Pentlandite occurring with

. Specimen from Sudbury,

. File:Pentlandite with Chalcopyrite (47700365072).jpg, Pentlandite occurring with

. Specimen from Sudbury,

. File:Pentlandite with Pyrrhotite and Chalcopyrite (47700373082).jpg, Pentlandite occurring with

and

. Specimen from Choate,

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

Etymology

Identification

Physical and optical properties

Mineral associations

Pentlandite group

Paragenesis

Occurrence

Gallery

See also

References

Further reading