The Mineral cuprite

Cuprite is named for the Latin cuprum, "copper", in allusion to its copper content. It can form as bright transparent red crystals, or as lustrous, submetallic opaque crystals. Even the opaque form will have slightly red edges and faint transparency upon back-lighting. Cuprite is often associated together with Native Copper in copper deposits, and frequently forms as an encrusting reddish coating over the Copper. Malachite is known to fully or partially coat a layer or pseudomorph over Cuprite, forming an interestingly shaped and a sometimes sparkling green crystal form.

Chemical Formula

Cu₂O

Color

Bright-red, maroon, brownish-red, dark red, purplish-red, reddish-black, dark gray

Crystal System

Isometric

Properties

Streak Brownish-red

Hardness 3.5 - 4

Transparency Translucent to opaque

Specific Gravity 6.1

Luster Adamantine or submetallic

Cleavage 3, all directions

Fracture Uneven

Tenacity Brittle

Crystal Habits

Usually in octahedral crystals or in groups of octahedral crystals, sometimes with modified cubic crystal edges. Less commonly cubic or in cubic clusters. Rarely in dodecahedral or modified dodecahedral form. Sometimes twinned as penetration twins, and occasionally in hopper growths. Also as masses of tiny elongated needles, capillary, fibrous, radiating, and massive. Commonly in a thin or encrusting coating upon Native Copper crystals. Crystals are often striated or have growth layers or patterns.

3D Crystal Atlas

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Additional Information

Composition Copper oxide

In Group Oxides; Simple Oxides

Striking Features Crystal shape, color and luster, and occurence in copper deposits.

Environment As a secondary mineral in the oxidation zone in hydrothermal copper-bearing replacement deposits.

Varieties

Chalcotrichite

 -   Variety of Cuprite composed of dense, hair-like or needle-like fibers.

Uses

Cuprite is an important collectors mineral, and is a minor ore of copper.

Noteworthy Localities

Some of the most outstanding lustrous dark red octahedral Cuprite crystals and groupings come from Kolwezi, Katanga (Shaba), Congo (Zaïre). Exceptionally large crystals, often coated with a shiny green coating of Malachite, are well-known from Ogonja, Seeis, Namibia; and a classic locality for fine Cuprite is Tsumeb, Namibia.

A relatively new Cuprite find producing outstanding lustrous dark gray octahedral crystal groupings is the Rubtsovoskoe Mine, near Poteryaevka, Altai, Russia. Cuprite crystals from this locality has become very popular among collectors. Fine sharp and lustrous octahedral Cuprite come from Dzezkazgan, Kazakhstan. In China, well-formed crystals and the Chalcocitrite variety have come from the Fengjiashan Mine, Daye, Hubei Province; and the Chengmenshan Mine, Jiurui, Jiangxi Province.

Bright cherry-red Cuprite crystals have come from the Red Dome Mine, Chillagoe, Queensland, Australia. Cornwall, England, is a classic producer, and this includes several localities in the Camborne/Redruth/St Day District; as well as Wheal Phoenix and Caradon, Linkinhorne, Liskeard District. In France, two noteworthy occurrences are Chessy, Rhône (especially noted for the Malachite pseudomorphs; and the Le Moulinal Mine, Paulinet.

In the U.S., excellent Cuprite specimens have come from many of the important copper deposits of Arizona, with the most notable and classic being Bisbee, Cochise Co. Other noteworthy Arizona localities are Ray, Pinal Co., Arizona; and the New Cornelia Mine, Ajo, Pima Co.

Common Mineral Associations

Copper, Malachite, Calcite, Chrysocolla, Limonite

Distingushing Similar Minerals

Spinel - Much greater in hardness, has white streak.
Sphalerite - Different crystal habits and mode of occurrence.
Rutile - Greater hardness and different crystal forms.

cuprite Photos

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