Cupalite is a rare mineral which is mostly composed of copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 and aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

, but might contain up to several percents of zinc

Zinc

Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 or iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

; its chemical structure is therefore described by an approximate formula (Cu,Zn)Al or (Cu,Fe)Al. It was discovered in 1985 in placers

Placer deposit

In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation during sedimentary processes. The name is from the Spanish word placer, meaning "alluvial sand". Placer mining is an important source of gold, and was the main technique used in the early...

 derived from serpentine, in association with another rare mineral khatyrkite

Khatyrkite

Khatyrkite is a rare mineral which is mostly composed of copper and aluminium, but might contain up to about 15% of zinc or iron; its chemical structure is described by an approximate formula Al2 or Al2. It was discovered in 1985 in placers derived from serpentine, in association with another...

 (CuAl₂). Both minerals are thus far restricted to the area of Listvenitovyi Stream, in the Khatyrka

Khatyrka

-External links:*...

 ultramafic (silicon

Silicon

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

-poor) zone of the Koryak–Kamchatka fold area, Koryak Mountains

Koryak Mountains

The Koryak Mountains are a mountain range in Far-Eastern Siberia, Russia, located south of the Anadyr River, and northeast of the Kamchatka Peninsula. Rivers Main and Velikaya have their sources in the Koryak Range. They are the second largest mountain range in all of Siberia....

, Beringovsky District

Beringovsky District

Beringovsky District was an administrative district of Chukotka Autonomous Okrug, Russia, which existed in 1957–2011. Municipally, together with Anadyrsky Administrative District, it was incorporated into Anadyrsky Municipal District...

, Chukotka Autonomous Okrug

Chukotka Autonomous Okrug

Chukotka Autonomous Okrug , or Chukotka , is a federal subject of Russia located in the Russian Far East.Chukotka has a population of 53,824 according to the 2002 Census, and a surface area of . The principal town and the administrative center is Anadyr...

, Far Eastern

Far Eastern Federal District

The Far Eastern Federal District is the largest of the eight federal districts of Russia, while being also the least populated, with a population of 6,291,900 . The Far Eastern Federal District was established in 2000 by then-President Vladimir Putin and is currently being governed by presidential...

 Federal District

Federal districts of Russia

The federal districts are a level of administration for the convenience of the federal government of the Russian Federation. They are not the constituent units of Russia . Each district includes several federal subjects and each federal district has a presidential envoy...

, Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. The mineral name derives from cuprum (Latin for copper) and aluminium. Its holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 (defining sample) is preserved in the Mining Museum

Saint Petersburg Mining Institute

The G. V. Plekhanov Saint Petersburg State Mining Institute and Technical University is Russia's oldest higher education institute devoted to engineering...

 in Saint Petersburg

Saint Petersburg

Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

, and parts of it can be found in other museums, such as Museo di Storia Naturale di Firenze

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...

.

Properties

Cupalite forms dendritic, rounded or irregular grains, typically below 0.1 millimeter in size, which are intergrown with khatyrkite. They have an orthorhombic

Orthorhombic crystal system

In crystallography, the orthorhombic crystal system is one of the seven lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base and height , such that a,...

 crystal structure with a yet uncertain space group

Space group

In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...

 and the lattice constants a = 0.695(1) nm, b = 0.416(1) nm, c = 1.004(1) nm, and 10 formula unit

Formula unit

A formula unit in chemistry is the empirical formula of an 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. Their Mohs hardness

Mohs scale of mineral hardness

The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...

 is between 4 and 4.5 and Vickers hardness

Vickers hardness test

The Vickers hardness test was developed in 1924 by Smith and 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 tests since the required calculations are independent of the size of the...

 is in the range 272–318 kg/mm² for a 20–50 gram load.

Cupalite and khatyrkite are accompanied by spinel

Spinel

Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...

, corundum

Corundum

Corundum is a crystalline form of aluminium oxide with traces of iron, titanium and chromium. It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red...

, stishovite

Stishovite

Stishovite is an extremely hard, dense tetragonal form of silicon dioxide. It was long considered the hardest known oxide; however, boron suboxide has recently been discovered to be much harder...

, augite

Augite

Augite is a single chain inosilicate mineral, 2O6. 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

Olivine

The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....

, diopsidic clinopyroxene and several Al-Cu-Fe metal alloy minerals. They are remarkable by containing micrometre-sized grains of the only known naturally occurring quasicrystal

Quasicrystal

A quasiperiodic crystal, or, in short, quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry...

– 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.