Cuprite

cuprite

copper

shattuckite

chalcocite

Images

Formula: Cu₂O
Oxide

Varieties

Chalcotrichite is an acicular variety of cuprite

Properties of cuprite

Specific gravity: 6.15
Hardness: 3½ to 4
Streak: Brownish red
Colour: Red
Solubility: Moderately soluble in hydrochloric acid; slightly soluble in sulphuric and nitric acid
Environments:

Hydrothermal environments

Cuprite is a secondary mineral found in the oxidation portions of high temperature copper deposits, associated with limonite and secondary copper minerals such as native copper, malachite, azurite and chrysocolla.
It may be found as an oxidation product coating native copper, or as an alteration product of chalcopyrite.

Localities

At the Mount Kelly deposit, Gunpowder District, Queensland, Australia, the deposit has been mined for oxide and supergene copper ores, predominantly malachite, azurite and chrysocolla. The ores overlie primary zone mineralisation consisting of quartz-dolomite-sulphide veins hosted in dolomite-bearing siltstone and graphitic schist.
Cuprite crystals to 2 mm occur, some pseudomorphing chalcopyrite and some encapsulated in calcite. The crystals commonly occur in small cavities and lining fractures in siliceous goethite-hematite rich gossan. The acicular variety chalcotrichite has also been found here (AJM 22.1.21).

At the M'sesa mine, Kambove District, Haut-Katanga, DR Congo, shattuckite pseudomorphs after cuprite have been found (KL p231).

At the Mashamba West Mine, Kolwezi mining district, Lualaba, DR Congo, shattuckite pseudomorphs after cuprite occur (R&M 87.4.304-336).

At Tsumeb, Namibia, cuprite occurs in dolomite ore, and pseudomorphs of malachite after cuprite have been recorded (R&M 93.6.542).

At the Rubtsovsk mine, Rubtsovsky District, Altai Krai, Russia, copper pseudomorphs after cuprite have been found (R&M 95.3.275).

At the Bardon Hill quarry, Coalville, Leicestershire, England, UK, cuprite occurs with native copper altering to chrysocolla and malachite (RES p193).

At New Cliffe Hill quarry, Stanton under Bardon, Leicestershire, England, UK, cuprite occurs with native copper and malachite (RES p197).

At the Cotopaxi Mine, Colorado, USA, cuprite crystals are found rimmed with green malachite. (R&M 84.6.547).

At the Chino mine, New Mexico, USA, cuprite occurs overgrown with goethite. (R&M 84.6.492-500).

Alteration

chalcocite, oxygen and water to cuprite and sulphuric acid 2S(s) + 2O₂(g) + H₂O(l) → Cu₂O(s) + H₂SO₄(aq)
If acidic copper sulphate solutions pass through the oxidation zone to below the water table, conditions usually change to reducing and the dissolved copper ions react with sulphide ions to form copper sulphides such as chalcocite. If the water table falls, allowing the chalcocite to be exposed to the oxidation zone, then cuprite may be formed according to the above equation (JRS 18.14).

The diagram below is a Pourbaix diagram for copper (GSJ). It shows the relationship between copper Cu, cuprite Cu₂O and spertiniite Cu(OH)₂.
























The diagram below is a Pourbaix diagram for Cu-Fe-S-H₂O (IJNM 07(02).9.23). It shows the relationship between copper Cu, chalcopyrite CuFeS₂, tenorite CuO, covellite CuS, cuprite Cu₂O, chalcocite Cu₂S, pyrite FeS₂ and hematite Fe₂O₃.
























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