Native copper is an element and a mineral. It is an uncombined form of copper that occurs as a natural mineral. It is rarely found in large quantities, thus it is seldom the primary target of a mining operation. 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. Most copper produced is extracted from sulfide deposits.
Native copper was an important ore of copper in historic times and was used by pre-historic peoples.
- Category: Native metal
- Formula: (repeating unit) Cu
- Crystal system: Cubic
- Crystal class: Hexoctahedral (m3m)
- Color: Pale rose on fresh surface, quickly darkens to copper-red; in reflected light, pale rose.
It has a reddish, orangish, and/or brownish color on fresh surfaces, but typically is weathered and coated with a green tarnish of copper(II) carbonate (also known as patina or verdigris). Its specific gravity is 8.9 and its hardness is 2.5–3.
- Crystal habit: As cubes, dodecahedra, and as tetrahexahedra; rarely as octahedra and complex combinations.
- Cleavage: None
- Fracture: Hackly – jagged
- Tenacity: Highly malleable and ductile
- Mohs scale hardness: 2 1⁄2–3
- Luster: Metallic
- Streak: Copper-red
- Diaphaneity: Opaque
- Specific gravity: 8.95
- Solubility: Soluble in nitric acid
Native copper occurs rarely as isometric cubic and octahedral crystals, but more typically as irregular masses and fracture fillings. It is found in the oxidized zones of copper deposits; in hydrothermal veins; in the cavities of basalt that have been in contact with hydrothermal solutions; and as pore fillings and replacements in conglomerates that have been in contact with hydrothermal solutions.
The mines of the Keweenaw native copper deposits of Upper Michigan were major copper producers in the 19th and early 20th centuries, and are the largest deposits of native copper in the world.
Copper is an excellent conductor of electricity. Most copper mined today is used to conduct electricity – mostly as wiring. It is also an excellent conductor of heat and is used in cooking utensils, heat sinks, and heat exchangers.