Copper

Copper was probably the first metal to be used by humans. Neolithic people are believed to have used as a substitute for stone by 8000 BCE. Around 4000 BCE, Egyptians cast copper in molds. By 3500 BCE, Its began to be alloyed with tin to produce bronze. It is opaque, bright, and metallic salmon pink on freshly broken surfaces but soon turns dull brown. Crystals are uncommon, but when formed are either cubic or dodecahedral, often arranged in branching aggregates. Most found as irregular, flattened, or branching masses. It is one of the few metals that occur in the “native” form without being bonded to other elements. Native copper seems to be a secondary mineral, a result of interaction between copper-bearing solutions and iron-bearing minerals.

Name: From the Latin cuprum, in turn from the Greek kyprios, Cyprus, from which island the metal was early produced.

Chemistry: Typically with only small amounts of other metals.

Association: Silver, chalcocite, bornite, cuprite, malachite, azurite, tenorite, iron oxides, many other minerals.

Chemical Properties

Copper is a chemical element with the symbol Cu and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. Here are some of the key chemical properties of copper:

1. Atomic number: 29
2. Atomic weight: 63.55
3. Density: 8.96 g/cm³
4. Melting point: 1,083 °C (1,981 °F)
5. Boiling point: 2,562 °C (4,644 °F)
6. Oxidation states: +1, +2
7. Electronegativity: 1.9
8. Ionization energy: 745.5 kJ/mol
9. Thermal conductivity: 401 W/(m·K)
10. Electrical conductivity: 59.6 × 10^6 S/m

Copper is also highly reactive with some acids and non-metals like oxygen and sulfur, which is why it often develops a greenish patina over time when exposed to air and moisture. This patina is actually a layer of copper carbonate that protects the underlying metal from further corrosion.

Physical Properties

Color	Red on a fresh surface, dull brown on a tarnished surface
Streak	Metallic copper red
Luster	Metallic
Cleavage	None
Diaphaneity	Opaque
Mohs Hardness	2.5 to 3
Specific Gravity	8.9
Diagnostic Properties	Color, luster, specific gravity, malleability, ductility
Crystal System	Isometric
Tenacity	Malleable
Fracture	Hackly
Density	8.94 – 8.95 g/cm3 (Measured)    8.93 g/cm3 (Calculated)

Optical Properties

Copper has some interesting optical properties that have made it useful in a variety of applications. Here are a few of its optical properties:

1. Color: Copper has a distinctive reddish-orange color when in its pure state, but it can also appear brown or gray depending on its surface finish and the presence of other elements or compounds.
2. Luster: Copper has a bright metallic luster, meaning that it reflects light well and appears shiny.
3. Transparency: Copper is not transparent to visible light, meaning that light cannot pass through it.
4. Reflectivity: Copper is highly reflective, meaning that it bounces light off its surface very effectively. This makes it useful in applications where reflection is desired, such as in mirrors.
5. Electrical conductivity: Copper is an excellent conductor of electricity, making it useful in electrical wiring and other applications where electricity needs to be conducted efficiently.
6. Thermal conductivity: Copper is also an excellent conductor of heat, making it useful in applications such as heat sinks and cooking pans.
7. Absorption spectra: Copper has distinct absorption spectra in the visible and infrared regions, which can be used for analysis and detection purposes.

Overall, copper’s optical properties make it a versatile material that is useful in a variety of applications.

Classification of Copper Minerals

Copper minerals can be classified based on their chemical composition and crystal structure. Some common classifications include:

1. Native copper: Copper that occurs in its pure metallic form, typically found as nuggets or wires.
2. Sulfides: Copper sulfide minerals include chalcopyrite (CuFeS2), bornite (Cu5FeS4), chalcocite (Cu2S), covellite (CuS), and enargite (Cu3AsS4).
3. Oxides: Copper oxide minerals include cuprite (Cu2O) and tenorite (CuO).
4. Carbonates: Copper carbonate minerals include malachite (Cu2CO3(OH)2) and azurite (Cu3(CO3)2(OH)2).
5. Silicates: Copper silicate minerals include chrysocolla (CuSiO3·2H2O) and dioptase (CuSiO2(OH)2).
6. Native elements: Copper can also occur in its pure metallic form as dendritic or wire-like structures.

These minerals can be found in a variety of geological settings, including porphyry copper deposits, volcanic-hosted massive sulfide deposits, sediment-hosted copper deposits, and skarn deposits.

Common Copper Minerals and their Properties

Here are some common copper minerals and their properties:

1. Chalcopyrite: This is the most common copper mineral, and it has the chemical formula CuFeS2. Chalcopyrite has a brassy yellow color, a metallic luster, and a hardness of 3.5-4 on the Mohs scale. It is often found with other sulfide minerals.
2. Bornite: Also known as peacock ore due to its iridescent purple-blue coloring, bornite has the chemical formula Cu5FeS4. It has a hardness of 3 on the Mohs scale and is often found in hydrothermal veins with other copper minerals.
3. Malachite: This green mineral has the chemical formula Cu2CO3(OH)2 and is formed by the weathering of copper ore deposits. It has a hardness of 3.5-4 on the Mohs scale and is often used as a decorative stone.
4. Azurite: This blue mineral has the chemical formula Cu3(CO3)2(OH)2 and is also formed by the weathering of copper ore deposits. It has a hardness of 3.5-4 on the Mohs scale and is often found in combination with malachite.
5. Cuprite: This red mineral has the chemical formula Cu2O and is formed by the oxidation of copper sulfides. It has a hardness of 3.5-4 on the Mohs scale and is often found in association with other copper minerals.
6. Covellite: This blue-black mineral has the chemical formula CuS and is often found in hydrothermal veins with other sulfide minerals. It has a hardness of 1.5-2.5 on the Mohs scale.
7. Tetrahedrite: This gray-black mineral has the chemical formula Cu12Sb4S13 and is often found in hydrothermal veins with other sulfide minerals. It has a hardness of 3-4 on the Mohs scale.

These are just a few examples of the many copper minerals that exist, and their properties can vary depending on their specific chemical composition and geological context.

Factors affecting copper mineralization

There are several factors that can influence the formation and concentration of copper mineralization, including:

1. Geology: The presence of suitable host rocks and favorable geological structures, such as faults or fractures, can provide pathways for mineralizing fluids to flow and deposit copper minerals.
2. Tectonic setting: Copper mineralization is often associated with regions of tectonic activity, such as subduction zones, where magma and hydrothermal fluids can be generated and transported to the Earth’s surface.
3. Temperature and pressure: Copper mineralization is generally associated with hydrothermal activity, which is influenced by temperature and pressure conditions. High-temperature and high-pressure conditions can facilitate the deposition of copper minerals.
4. Fluid chemistry: The chemical composition of mineralizing fluids, including their pH, oxidation state, and the concentration of metals and ligands, can affect the solubility and deposition of copper minerals.
5. Time: The longer a mineralizing system is active, the greater the opportunity for copper minerals to accumulate and form economically viable deposits.

Exploration methods for copper minerals

Exploration for copper minerals usually involves a combination of techniques, including geologic mapping, geochemical sampling, geophysical surveys, and drilling.

Geologic mapping involves the detailed examination and mapping of surface rocks and outcrops to identify the geological features associated with copper mineralization, such as alteration zones, veins, and breccias.

Geochemical sampling involves the collection and analysis of rock, soil, and water samples to detect anomalous concentrations of copper and other elements associated with mineralization.

Geophysical surveys use various methods, including magnetic, gravity, and electromagnetic surveys, to detect changes in the physical properties of rocks that may indicate the presence of copper mineralization.

Drilling is used to test and confirm the presence and extent of copper mineralization at depth. Diamond drilling is the most common method, but other methods such as reverse circulation drilling may also be used.

Modern exploration techniques also use remote sensing technologies, such as satellite imagery and aerial photography, to help identify potential areas for further exploration.

Occurrence

Copper is a relatively abundant element in the Earth’s crust, with an estimated concentration of about 50 parts per million (ppm). It is found in various minerals, including chalcopyrite (CuFeS2), bornite (Cu5FeS4), chalcocite (Cu2S), cuprite (Cu2O), malachite (Cu2CO3(OH)2), and azurite (Cu3(CO3)2(OH)2), among others.

Copper deposits are typically formed by hydrothermal processes associated with igneous activity. These processes involve the circulation of hot, mineral-rich fluids through fractures and other openings in the surrounding rock. As the fluids cool, the minerals they carry are deposited in veins, fractures, and other structural features.

Copper is also found in sedimentary rocks and in some deposits associated with volcanic activity. In addition, copper can be found in trace amounts in seawater, although the concentration is too low to be economically viable for mining.

Geological settings of copper mineralization

Copper mineralization can occur in a variety of geological settings, but the most common ones include:

1. Porphyry copper deposits: These are the world’s most important sources of copper and are associated with large, intrusive igneous rocks. Porphyry copper deposits form in the shallow crust (within 1-6 km depth) when hot, metal-rich fluids rise from cooling magma chambers and encounter cooler rock, causing copper and other metals to precipitate in the surrounding rock.
2. Sediment-hosted copper deposits: These deposits occur within sedimentary rocks that were deposited in marine or lacustrine environments. The copper is usually associated with shale, sandstone, and carbonate rocks, and the deposits can be stratiform (parallel to the bedding) or structurally controlled.
3. Volcanogenic massive sulfide (VMS) deposits: These are typically small to medium-sized deposits that form at or near the seafloor in volcanic or sedimentary rocks. They are characterized by high grades of copper, zinc, lead, and other metals, and are often associated with hydrothermal vents on the seafloor.
4. Copper skarns: These are hydrothermal deposits that occur in carbonate rocks, typically near intrusions of granitic or dioritic rocks. Skarn deposits are usually characterized by high grades of copper, as well as significant amounts of other metals such as gold, silver, and molybdenum.
5. Copper oxide deposits: These deposits are usually found near the surface and are formed by weathering and oxidation of copper sulfide minerals. They typically occur in arid or semi-arid regions, where copper minerals are leached from the rocks by acidic groundwater and accumulate in the form of copper oxide minerals.

These are just a few of the most common geological settings for copper mineralization, and there are many others as well.

Importance of copper minerals

Copper minerals are important because they are the primary source of copper metal, a valuable industrial metal used in a wide range of applications. Copper is an excellent conductor of electricity and is widely used in the electrical and electronics industries for wiring, motors, generators, and other equipment. Copper is also used in construction, plumbing, and heating systems due to its high thermal conductivity and resistance to corrosion. Additionally, copper is used in the production of brass and bronze, two important alloys used in the manufacture of various products. Copper is also an essential nutrient for human health, with a range of biological roles in the body, including the formation of red blood cells and the maintenance of healthy connective tissue.

Uses Area

Copper has a wide range of uses in various industries and applications due to its excellent electrical conductivity, malleability, ductility, and corrosion resistance. Some of the major areas where copper is used include:

1. Electrical industry: Copper is a highly conductive metal and is widely used in electrical wiring, power generation, and transmission. It is also used in the production of motors, transformers, switches, and other electrical equipment.
2. Construction industry: Copper is used in plumbing, roofing, and cladding due to its corrosion resistance and durability. It is also used in heating, ventilation, and air conditioning systems.
3. Automotive industry: Copper is used in the production of radiators, heat exchangers, and electrical wiring.
4. Electronics industry: Copper is used in the production of printed circuit boards, computer chips, and other electronic components.
5. Medical industry: Copper is used in medical equipment, such as X-ray machines, due to its excellent electrical conductivity and radiopacity.
6. Coinage: Copper is used in the production of coins due to its durability and resistance to corrosion.
7. Decorative applications: Copper is used in jewelry, sculptures, and other decorative applications due to its attractive reddish-brown color and malleability.
8. Antimicrobial properties: Copper has natural antimicrobial properties and is used in the production of hospital equipment, door handles, and other high-touch surfaces to reduce the spread of infections.

Overall, copper is a versatile metal with a wide range of uses in various industries and applications.

Global distribution of copper minerals

Copper minerals are found in many parts of the world, and copper production is a major industry in many countries. The top copper producing countries in the world include Chile, Peru, China, the United States, Australia, the Democratic Republic of Congo, Zambia, Russia, and Canada.

Chile is the world’s largest copper producer, accounting for approximately 28% of global copper production in 2020. Peru is the second largest producer, followed by China and the United States. Other significant copper producing countries include Indonesia, Mexico, Kazakhstan, and Poland.

Copper minerals are typically found in association with other minerals such as gold, silver, lead, and zinc, and are often extracted as by-products of these other metals. Some of the most important copper mineral deposits in the world include the Chuquicamata mine and the Escondida mine in Chile, the Grasberg mine in Indonesia, and the Olympic Dam mine in Australia.

• In the USA, as remarkably large masses and excellent, large crystals in deposits of the Keweenaw Peninsula, Keweenaw and Houghton Cos., Michigan; in several porphyry deposits in Arizona including those at the New Cornelia mine, Ajo, Pima Co.; the Copper Queen and other mines at Bisbee, Cochise Co.; and at Ray, Gila Co.; similarly in the Chino mine at Santa Rita, Grant Co., New Mexico.
• In Namibia, at the Onganja mine, 60 km northeast of Windhoek, and at Tsumeb.
• In large crystals from the Turinsk mine, Bogoslovsk, Ural Mountains, Russia.
• In Germany, at Rheinbreitbach, North Rhine-Westphalia, and the Friedrichssegen mine, near Bad Ems, Rhineland-Palatinate.
• In fine specimens from many mines in Cornwall, England.
• In Australia, at Broken Hill, New South Wales.
• In Chile, at Andacolla, near Coquimbo. From Bolivia, at Corocoro.

Copper demand and production trends

Copper is a widely used metal with a broad range of applications, including electrical wiring, plumbing, construction, and electronics. As a result, global demand for copper is heavily influenced by trends in these industries.

Over the past several decades, copper demand has steadily increased due to the growing use of electronic devices, infrastructure development in emerging economies, and the electrification of transportation. According to the International Copper Study Group (ICSG), global copper consumption grew at an average annual rate of 3.4% between 2000 and 2019.

Copper production has also increased to meet this growing demand. The largest producers of copper are Chile, Peru, China, the United States, and the Democratic Republic of Congo. In 2020, global copper mine production was estimated to be around 20 million metric tons.

However, copper production can be affected by various factors, such as natural disasters, labor strikes, and fluctuations in commodity prices. For example, the COVID-19 pandemic in 2020 led to a temporary decline in copper production due to mine closures and supply chain disruptions.

Overall, the demand for copper is expected to continue to increase in the coming years, driven by the growth of renewable energy, electric vehicles, and other high-tech applications.

References

Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
Mindat.org. (2019). Copper: Mineral information, data and localities..
Available at: https://www.mindat.org/min-727.html [Accessed 4 Mar. 2019].