Cuprite

minerals

copper

shattuckite

chalcocite

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Formula: Cu2O
Oxide
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.

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.

Pourbaix copper.jpg






















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.

Pourbaix Cu-Fe-S-H<sub>2</sub>O.jpg






















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