Skaergaardite is an intermetallic

platinum group The platinum-group metals (abbreviated as the PGMs; alternatively, the platinoids, platinides, platidises, platinum group, platinum metals, platinum family or platinum-group elements (PGEs)) are six noble, precious metallic elements clustered to ...

mineral with the general chemical formula Pd Cu. The mineral is named after its discovery location: the

Skaergaard intrusion The Skaergaard intrusion is a layered igneous intrusion in the Kangerlussuaq area, East Greenland. It comprises various rock types including gabbro, ferro diorite, anorthosite and granophyre. Discovered by Lawrence Wager in 1931 during the Br ...

, Kangerdlugssuaq area, East

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

. The mineral name was approved by the

International Mineralogical Association Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 5000 plus known mineral species. Th ...

in 2003. The mineral has also been reported in the Duluth intrusion in

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

and the

Rum layered intrusion The Rum layered intrusion is located in Scotland, on the island of Rùm ( Inner Hebrides). It is a mass of intrusive rock, of mafic-ultramafic composition, the remains of the eroded, solidified magma chamber of an extinct volcano that was active ...

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

Occurrence

Skaergaardite is associated with igneous intrusions containing well-preserved, oxide-rich,

tholeiitic The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma i ...

gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is che ...

. It is found as inclusions in titanian

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 the ...

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

pyroxenes The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

, and

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...

. Skaergaardite can occur as an inclusion by itself, but is more commonly found in composite microglobule inclusions of copper iron

sulfide mineral The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide (S22−) as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides, the ...

s and other precious metal bearing minerals.

Crystallography and symmetry

The crystallography of skaergaardite was determined using

x-ray powder diffraction An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 ...

data. It has an isometric (cubic) crystal system and a hexoctahedral crystal class (

Hermann–Mauguin notation In geometry, Hermann–Mauguin notation is used to represent the symmetry elements in point groups, plane groups and space groups. It is named after the German crystallographer Carl Hermann (who introduced it in 1928) and the French mineralogis ...

: 4/m2/m). Skaergaardite can appear in various forms including: droplets; cubic grains with rounded outlines; euhedral to subhedral grains; and irregular grains or aggregates.

Optical properties

When viewed under a microscope in plane polarized light, skaergaardite appears to be bright creamy white (in the presence of

bornite Bornite, also known as peacock ore, is a sulfide mineral with chemical composition Cu5 Fe S4 that crystallizes in the orthorhombic system (pseudo-cubic). Appearance Bornite has a brown to copper-red color on fresh surfaces that tarnishes to v ...

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 hardness of 3.5 to 4 on the Mo ...

) or bright white (in the presence of

digenite Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal - hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic f ...

chalcocite Chalcocite (), copper(I) sulfide (Cu2S), is an important copper ore mineral. It is opaque and dark gray to black, with a metallic luster. It has a hardness of 2.5–3 on the Mohs scale. It is a sulfide with a monoclinic crystal system. The ...

). When the mineral is rotated on the microscope stage its color does not change, indicating that it is non-pleochroic. Under crossed polar light, skaergaardite appears completely dark no matter the direction the stage is rotated, indicating that the mineral is isotropic. As skaergaardite is isotropic, it is also non-birefringent.Klein, C., and Dutrow, B. (2007) The 23rd Edition of the Manual of Mineral Science. John Wiley and Sons, Inc. Hoboken, New Jersey, U.S.A.

Importance

Skaergaardite contains

palladium Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...

(Pd), one of the six

metals (PGM) that are some of the rarest elements on earth.Powell, D, 2000, "Platinum Group." Mineral Information Institute. . Accessed 23 November 2010. With the cost of palladium expected to increase as demand becomes greater, Skaergaardite could begin to be mined for its valuable palladium resources.Brooks, K. (2005) The Skaergaard intrusion: from icon to precious metal deposit. Geology Today, 21, 218-221. The Skaergaard intrusion is the only known source of skaergaardite large enough to be mined. Skaergaardite is the most common PGM mineral in the intrusion, making up over 90% of all the PGM observed. The most mineral-rich layer of the intrusion could contain over 1000 tons of skaergaardite. In addition to palladium:

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...

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". Platinu ...

, and other precious metals have been found in the intrusion. Interest has been increasing for an underground mine in the Skaergaard intrusion. A pre-feasibility study is currently under way and is scheduled for completion by December 2011.Platina Resources Limited, 7 October 2009, "Skaergaard Gold-PGM Project Moves To Next Stage Following Positive Scoping Study Review." . Accessed 23 November 2010.

References

{{Reflist Copper minerals Palladium minerals Cubic minerals Minerals in space group 221