Cupalite is a rare mineral which is mostly composed 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 pinkish ...
and
aluminium
Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...
, but might contain up to several percent of
zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic t ...
or
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) 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, right in ...
;
its chemical structure is therefore described by an approximate formula or . It was discovered in 1985 in
placers derived from
serpentine, in association with another rare mineral
khatyrkite
Khatyrkite ( ) is a rare mineral which is mostly composed of copper and aluminium, but may contain up to about 15% of zinc or iron. Its chemical structure is described by an approximate formula or . It was discovered in 1985 in a placer in assoc ...
(CuAl
2). Both minerals are thus far restricted to the area of the
Iomrautvaam, in the
Khatyrka
Khatyrka (russian: Хатырка; ckt, Ватыркан, ''Vatyrkan'') is a rural locality (a '' selo'') in Anadyrsky District of Chukotka Autonomous Okrug, Russia,Directive #617-rp located on the shore of the Bering Sea southwest of Beringo ...
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 compos ...
(
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...
-poor) zone of the Koryak–Kamchatka fold area,
Koryak Mountains
The Koryak Mountains or Koryak Highlands () are an area of mountain ranges in Far-Eastern Siberia, Russia, located in Chukotka Autonomous Okrug and in Kamchatka Krai, with a small part in Magadan Oblast. The highest point in the system is the Mou ...
,
Anadyrsky District
Anadyrsky District (russian: Ана́дырский райо́н; Chukchi: , ''Kagyrgyn rajon'') is an administrativeLaw #33-OZ and municipalLaw #148-OZ district (raion), one of the six in Chukotka Autonomous Okrug, Russia. It is located in the c ...
,
Chukotka Autonomous Okrug
Chukotka (russian: Чуко́тка), officially the Chukotka Autonomous Okrug,, ''Čukotkakèn avtonomnykèn okrug'', is the easternmost federal subject of Russia. It is an autonomous okrug situated in the Russian Far East, and shares a bo ...
,
Far Eastern
The ''Far East'' was a European term to refer to the geographical regions that includes East and Southeast Asia as well as the Russian Far East to a lesser extent. South Asia is sometimes also included for economic and cultural reasons.
The ter ...
Federal District
A federal district is a type of administrative division of a federation, usually under the direct control of a federal government and organized sometimes with a single municipal body. Federal districts often include capital districts, and they ...
,
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...
.
[Razin, L.V., N.S. Rudashevskii, and L.N. Vyal'sov. (1985) New natural intermetallic compounds of aluminum, copper and zinc – khatyrkite CuAI2, cupalite CuAI and zinc aluminides – from hyperbasites of dunite-harzburgite formation. Zap. Vses. Mineral. Obshch., 114,90–100 (in Russian). c.f. (1986) Amer. Mineral., 71, 1278] The mineral name derives from ''cup''rum (Latin for copper) and ''al''uminium. Its
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...
(defining sample) is preserved in the
Mining Museum
A mine, i.e. an industrial facility for the underground extraction of mineral commodities
In economics, a commodity is an economic good, usually a resource, that has full or substantial fungibility: that is, the market treats instances of the ...
in
Saint Petersburg
Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...
, and parts of it can be found in other museums, such as
Museo di Storia Naturale di Firenze
The Museo di Storia Naturale di Firenze is a natural history museum in 6 major collections, located in Florence, Italy. It is part of the University of Florence. Museum collections are open mornings except Wednesday, and all day Saturday; an adm ...
.
[
]
Properties
Cupalite forms dendritic, rounded or irregular grains, typically below 0.1 millimeter in size, which are intergrown with khatyrkite. They have an orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with ...
crystal structure with a yet uncertain space group
In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it ...
and the lattice constants ''a'' = 0.695(1) nm, ''b'' = 0.416(1) nm, ''c'' = 1.004(1) nm, and 10 formula unit
In chemistry, a formula unit is the empirical formula of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound. ...
s per unit cell
In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessari ...
. Their Mohs hardness
The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material.
The scale was introduced in 1812 by the ...
is between 4 and 4.5 and Vickers hardness
The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers test is often easier to use than other hardness ...
is in the range 272–318 kg/mm2 for a 20–50 gram load.spinel
Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , which means ''spine'' in reference to its pointed crystals.
Properties
...
, corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the ...
, stishovite
Stishovite is an extremely hard, dense tetragonal form ( polymorph) of silicon dioxide. It is very rare on the Earth's surface; however, it may be a predominant form of silicon dioxide in the Earth, especially in the lower mantle.
Stishovite wa ...
, augite
Augite is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees.
Characteristics
Augite is a solid solution in the pyroxene group ...
, forsteritic olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...
, diopsidic clinopyroxene
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 several Al-Cu-Fe metal alloy minerals. They are remarkable by containing micrometre-sized grains of icosahedrite
Icosahedrite is the first known naturally occurring quasicrystal phase. It has the composition Al63Cu24Fe13 and is a mineral approved by the International Mineralogical Association in 2010. Its discovery followed a 10-year-long systematic search ...
, a naturally occurring quasicrystal
A quasiperiodic crystal, or quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry. While crystals, according to the classical ...
– aperiodic, yet ordered structure. The quasicrystal has a composition of Al63Cu24Fe13 and icosahedral symmetry. The presence of unoxidized aluminium in cupalite and association with the stishovite – a form of quartz which forms exclusively at high pressures of several tens GPa – suggest that cupalite is formed either upon meteoritic impact or in the deep earth mantle.[
*]
References
{{reflist
Native element minerals
Copper minerals
Aluminium minerals
Orthorhombic minerals
Geology of Russia