Copper - Encyclopedia

    Class : Elements
    Subclass : Metals
    Crystal system : Cubic
    Chemistry : Cu
    Rarity : Common


Copper, or native copper, is a secondary mineral typical of the oxidation and cementation zone of copper sulphide deposits, where it is associated with cuprite, azurite, malachite, chalcocite... More rarely, it is a primary mineral in certain basic lavas, associated with native silver and arsenides (Michigan deposit). It takes its name from the Latin cuprum, previously cyprium aes (Cyprus bronze), an island where this metal was mined in Antiquity. It rarely forms sharp crystals ; these are then cubic, dodecahedral, hexatetrahedral often deformed and reaching up to 15 cm. Copper is usually found in dendrites of small, flattened, twisted crystals, generally passing into filiform or arborescent aggregates ("fern leaves"), in "leaves", or in sometimes imposing dendritic masses (up to 420 tons in Michigan ). It commonly pseudomorph other copper minerals (oxides and sulfides) and sometimes even carbonates (aragonite). Like most metals, copper is very malleable. Bright pink in color with a bright metallic luster when it is fresh, it quickly tarnishes to red, turns to brown, then to black. The Michigan deposits were the only industrial holdings of native copper as copper ore, and were the world's largest source of this metal from 1850 until the 1920's. Currently copper is mainly extracted from sulphide (bornite, chalcopyrite, chalcocite) and oxides (cuprite, tenorite), native copper only constituting a very secondary source of this metal. It can occasionally be cut into cabochon for jewelry.

Native copper from Itauz Mine, Kazakhstan
Native copper from Bou Nahas, Oumjrane, Er Rachidia, Morocco
Aragonite pseudomorph after copper from Coro Coro Mine, Bolivia
Native copper and cuprite from Poteryaevskoe Mine, Russia

Copper in the World

The most beautiful groups of crystals come from Michigan (Keweenaw peninsula), and Arizona (superb crystals from the New Cornelian and Copper Queen mines), from the Dzhezkazgan mine (Kazakhstan) and Russian mines from the Urals (Nijni Taguil especially). Beautiful twig masses come from Cornwall (Botallack).

Copper in France

In France, small clusters, sometimes spectacular, have been extracted from the Mine of St-Véran (Hautes-Alpes), that of Daluis (Alpes Maritime), as well as the fluorite mines of Albigeois (Le Burc, Le Moulinal, Montroc). Native copper is also naturally found on the Chessy copper mine (Rhône).

Twinning

Copper twinning run on {111} (spinel twin law).

Fakes and scams

Some arborescent crystals can be glued on matrix.



Hardness : 2.5 to 3
Density : 3.97
Fracture : -
Trace : Pink



TP : Opaque
RI : Not measurable
Birefringence : None
Optical character : None
Pleochroism : None
Fluorescence : None


Solubility : Nitric acid

Magnetism : Diamagnetic
Radioactivity : None