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 pink ...

and

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

, 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 periodi ...

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 (CuAl₂). Both minerals are thus far restricted to the area of the

Iomrautvaam The Iomrautvaam (russian: Иомраутваам; ckt, Емрауткенваам) is a river in Chukotka Autonomous Okrug, Russia. The length of the river is and the area of is drainage basin . The Iomrautvaam is the longest tributary of the ...

, 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 Beringovsk ...

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 composed ...

(

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 subjects of Russia, federal subject of Russia. It is an autonomous okrug situated in the Russian ...

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-ei ...

.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, has three operating phases: it may be open or running, or closed or it may be a working museum. Most mines are simply closed once they are no longer product ...

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.

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 uncha ...

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. E ...

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 necessaril ...

. 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 ...

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. Cupalite and khatyrkite are accompanied by

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 S ...

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 pr ...

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 ...

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 I ...

and several Al-Cu-Fe metal alloy minerals. They are remarkable by containing micrometre-sized grains of icosahedrite, 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