Copper

Mineral Name: Copper

Chemical Composition: Cu

Color: Red to brown; although, as oxidation occurs, copper tarnishes dark grey or blue. Further oxidation processes lead to a green (sometimes blue, brown, red, or black) tarnish. (2,4)

Streak: Copper-red, shiny

Hardness: 2.5-3

Cleavage/Fracture: Copper is commonly found as brown with sharp, jagged points, which geologists describe as hackly fracture.

Crystal Form: Copper can contain isometric crystals that have three equal axes that all lay 90 degrees from each other. In geology this is referred to as being, “isometric”. Crystals, however, are uncommon but when found will be in a face-centered, cubic configuration or dodecahedral, and uncommonly as octahedral crystals (1,2). Copper also occurs as scales (seen as fish-scale looking aggregates), dendrites (tree-like or skeletal shape), or wires (wiry aggregates). (2)

Luster: Metallic

Special Features: Copper is electrically conductive and transfers thermal energy; its unique atomic structure allows electric currents to pass through samples because its atomic lattice contains free electrons. Copper is also able to withstand an extensive range of temperatures and it hard to corrode in most environments. (1) Copper is extremely malleable and ductile (being able to be stretched into thin wires) (2). Copper’s ability to be molded makes it extremely durable and able to withstand weathering.

Varieties: Halfbreed, which is a mixture of copper and silver. This term can also be used to describe mixed copper and silver alloys (14).

Mineral Group: Copper is a metallic native element. Native elements are defined as having molecular structures of only one element (16). Metallic native elements, like gold, copper, and silver, are defined as electrically conductive, possess a metallic luster, and are malleable and ductile. They are considered true metals (15). Metallic native elements are found in the periodic table group of the transition metals (16).

Environment: Copper is extremely common especially in North and South America, Indochina and Southeast Asia. Copper is mostly found with gold, silver, lead or zinc or other metallic minerals. Copper is in rocks, water, soil, and sediments. It exists in trace amounts in the air and every plant and animal (11). It is unlikely to be found in large quantities but is particularly prevalent in cavities of basalt that have been exposed to hydrothermal solutions (8).

Associated Rock types: Copper can be found in igneous rocks such as basalt and tuff. Copper is also present in sedimentary rocks such as conglomerate, limestone, and sandstone. Deposits of copper in large quantities is referred to as copper ore.

Occurrence in North America: 9% of all copper mining occurs in North America, specifically in Michigan’s Keweenaw Peninsula (7). Other large copper mines are found in Arizona and New Mexico (13).

Economic Uses: Copper has been used in a wide array of items throughout recorded history. Although not an exhaustive list, copper has been used and manipulated into coins, statues, artwork, cookware, clocks, musical instruments, jewelry, weapons, and multiple household items such as door knobs and decorations. (12) Humans manipulated copper by burning it, cooling it and even smelting it.

In 4500 B.C., humans discovered how to smelt copper and how to make alloys out of copper. Bronze was born when humans decided to add zinc and tin to copper. Since it was such a huge and important discovery, humans now call the period after the creation of bronze the “Bronze Age”. (19)

Industrial Uses: Copper is used in building construction, irrigation equipment, power generation, and transmission, electronic product manufacturing, and the production of industrial machinery and transportation vehicles. Copper is an essential component in motors, wiring, radiators, connectors, breaks, and bearings used in cars and trucks. (12) Copper wiring is one of the main products that copper is used for in the United States. Copper is drawn into different gauges of wire because it is thin and malleable.

First Notable Identification: A copper pendant was found in northern Iraq and is believed to be from 8700 B.C., more than 10,000 years old (cite). Copper is also one of the first metals to be used/manipulated by ancient civilizations (8). The word copper is derived from Greek “kyprios” of Cyprus, the location of ancient copper mines; Latin “cuprum.” (10)

How We Identified It: We identified copper initially because of its red to dull brown color. Also, we identify copper through its streak that is copper red and features a metallic luster (8).

Don’t Confuse It With: Copper has many synthetic alloys, but the main ones are brass and bronze. Brass is an alloy that is mixed from copper and zinc that, when compared to copper itself, has more of a shiny gold finish. It is strong, and because of the zinc, it is slightly magnetic. Bronze on the other hand, is more dull and somewhat darker and is made from copper and tin. Bronze is tough, durable and is water-resistant. The tone and color are what separates the two alloys from copper and from each other.