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Cuprite is an oxide mineral composed of
copper(I) oxide Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper, the other being or copper(II) oxide or cupric oxide (CuO). This red-coloured solid is a component of some antifoulin ...
Cu2O, and is a minor
ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...
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 pinkis ...
. Its dark crystals with red internal reflections are in the isometric system hexoctahedral class, appearing as cubic, octahedral, or dodecahedral forms, or in combinations. Penetration
twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...
frequently occur. In spite of its nice color it is rarely used for
jewelry Jewellery ( UK) or jewelry ( U.S.) consists of decorative items worn for personal adornment, such as brooches, rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a w ...
because of its low
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 t ...
of 3.5 to 4. It has a relatively high
specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its densest ...
of 6.1, imperfect cleavage and is brittle to conchoidal fracture. The luster is sub-metallic to brilliant adamantine. The "chalcotrichite" (from grc, χαλκός θρίξ τριχός, "plush copper ore") variety typically shows greatly elongated (parallel to 01 capillary or needle like crystals forms. It is a secondary mineral which forms in the oxidized zone of copper sulfide deposits. It frequently occurs in association with
native copper Native copper is an uncombined form of copper that occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements. Native coppe ...
,
azurite Azurite is a soft, deep-blue copper mineral produced by weathering of copper ore deposits. During the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France. The mineral, a basic carb ...
,
chrysocolla Chrysocolla ( ) is a hydrated copper phyllosilicate mineral and mineraloid with formula (x<1) or . The structure of the mineral has been questioned, as a 2006 spectrographic study suggest material identified as ...
,
malachite Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2. This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fracture ...
, tenorite and a variety of iron oxide minerals.Hurlbut, Cornelius S.; Klein, Cornelis, 1985, ''Manual of Mineralogy,'' 20th ed., Wiley, p. 299-300 It is known as ''ruby copper'' due to its distinctive red color. Cuprite was first described by Wilhelm Karl Ritter von Haidinger in 1845 and the name derives from the
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
''cuprum'' for its copper content. Cuprite is found in the
Ural Mountains The Ural Mountains ( ; rus, Ура́льские го́ры, r=Uralskiye gory, p=ʊˈralʲskʲɪjə ˈɡorɨ; ba, Урал тауҙары) or simply the Urals, are a mountain range that runs approximately from north to south through western ...
, Altai Mountains, and
Sardinia Sardinia ( ; it, Sardegna, label=Italian, Corsican and Tabarchino ; sc, Sardigna , sdc, Sardhigna; french: Sardaigne; sdn, Saldigna; ca, Sardenya, label=Algherese and Catalan) is the second-largest island in the Mediterranean Sea, after ...
, and in more isolated locations in
Cornwall Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...
,
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
,
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
,
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
, Bolivia, and
Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
.Joel E. Arem, Ph.D., F.G.A., ''Color Encyclopedia of Gemstones'', 1977, Van Nostrand Reinhold Company


Cuprite as a gemstone

Though almost all crystals of cuprite are far too small to yield faceted
gemstones A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...
, one unique deposit from Onganja in Seeis,
Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
, which was discovered in the 1970s, has produced crystals which were both large and gem quality. Virtually every faceted stone over one carat (0.2 gm) in weight is from this single deposit, which has long since been mined out. The number of faceted gems over two carats (0.4 gm) is difficult to estimate, but according to Joel Arem, one-time curator for the Smithsonian National Gem and Mineral Collection in
Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
, faceted cuprite of any size is considered one of the most collectible and spectacular gems in existence, with its deep garnet coloring and higher brilliance than a diamond. Only the gem's soft nature prevents it from being among the most valuable jewelry stones.


See also

*
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 ...
* Tenorite CuO *
Tennantite Tennantite is a copper arsenic sulfosalt mineral with an ideal formula . Due to variable substitution of the copper by iron and zinc the formula is . It is gray-black, steel-gray, iron-gray or black in color. A closely related mineral, tetrahedri ...
* Tetrahedrite


References

{{Reflist Copper ores Alchemical substances Oxide minerals Cubic minerals Minerals in space group 224 Luminescent minerals