Per capita income
Per capita income or average income measures the average income earned per person in a given area in a specified year. It is calculated by dividing the area's total income by its total population. Per capita income is national income divided by population size. Per capita income is used to measure an area's average income and compare the wealth of different populations. Per capita income is used to measure a country's standard of living, it is expressed in terms of a used international currency such as the euro or United States dollar, is useful because it is known, is calculable from available gross domestic product and population estimates, produces a useful statistic for comparison of wealth between sovereign territories. This helps to ascertain a country's development status, it is one of the three measures for calculating the Human Development Index of a country. In the United States, it is defined by the U. S. Census Bureau as the following: "Per capita income is the mean money income received in the past 12 months computed for every man and child in a geographic area."
Critics claim that per capita income has several weaknesses in measuring prosperity: Comparisons of per capita income over time need to consider inflation. Without adjusting for inflation, figures tend to overstate the effects of economic growth. International comparisons can be distorted by cost of living differences not reflected in exchange rates. Where the objective is to compare living standards between countries, adjusting for differences in purchasing power parity will more reflect what people are able to buy with their money, it does not reflect income distribution. If a country's income distribution is skewed, a small wealthy class can increase per capita income while the majority of the population has no change in income. In this respect, median income is more useful when measuring of prosperity than per capita income, as it is less influenced by outliers. Non-monetary activity, such as barter or services provided within the family, is not counted; the importance of these services varies among economies.
Per capita income does not consider whether income is invested in factors to improve the area's development, such as health, education, or infrastructure. List of countries by average wage List of countries by GDP per capita—GDP at market or government official exchange rates per inhabitant List of countries by GDP per capita—GDP calculated at purchasing power parity exchange per inhabitant List of countries by GNI per capita List of countries by GNI per capita List of countries by income equality Total personal income
Peoria is a city in Maricopa and Yavapai counties in the State of Arizona. Most of the city is located in Maricopa County, while a tiny portion in the north is in Yavapai County, it is a major suburb of Phoenix. According to 2017 Census Bureau estimates, the population of the city is 168,181. Peoria is the sixth largest city in Arizona for land area, the ninth largest for population, it was named after Illinois. The word "peoria" is a corruption of the Illini word for "prairie fire." It is the spring training home of the San Diego Padres and Seattle Mariners, who share the Peoria Sports Complex. In July 2008, Money magazine listed Peoria in its Top 100 Places to Live. Peoria sits in the Salt River Valley, extends into the foothills of the mountains to the north. William John Murphy, who had worked on the Arizona Canal, recruited settlers to begin a community in Arizona, many of them from Peoria, Illinois. Albert J. and Elizabeth Straw were the first to establish residency in November 1886. They were followed by William T. and Sylvia Hanna, James M. and Clara Copes, James and Ella McMillan, all from Peoria, Illinois relocate to what is now Peoria, Arizona.
An old desert road connecting Phoenix to the Hassayampa River near present-day Wickenburg was the only major transportation route in the area until 1887, when a new road was laid out. Named Grand Avenue, this road angled through the newly designed town sites of Alhambra and Peoria and became the main route from Phoenix to Vulture Mine; the settlers filed Peoria's plot map with the Maricopa County recorder on May 24, 1897, naming the settlement after their hometown. The original plot map of Peoria included east and west streets Monroe, Jefferson, Jackson, Lincoln and Van Buren. Streets going north and south were Almond, Orange, Walnut, the plot was from present-day Peoria and 85th avenues to Monroe Street and 85th Avenue to Monroe Street and 81st Avenue to 81st Avenue and south of the Desert Cove alignment. On August 4, 1888, the Territory of Peoria, Arizona was granted a post office in its name and served a population of 27. Maricopa County supervisors defined the boundaries for School District Eleven, comprising forty-nine square miles, the first class took place in an unoccupied brick store that faced north on Washington Street until Peoria's first school building, a one-room structure completed in 1891.
Between 1891 and 1895 a spur line of the Santa and Phoenix Railroad was placed in Peoria along with Phoenix, Alhambra and Marinette. A small depot on 83rd Avenue just off Grand Avenue; the depot was sold to the city of Scottsdale in 1972 where it now resides at McCormick Stillman Railroad Park. About 1919 the Peoria Chamber of Commerce formed, it operated as the informal government body until Peoria was incorporated in 1954. The Peoria volunteer fire district remained all volunteer until the mid-1950s; the three-story Edwards Hotel was built in 1918, followed by the Mabel Hood building in May 1920 at the southwest corner of Washington Street and 83rd Avenue. The John L. Meyer or "flatiron" building was completed in June 1920 and the O. O. Fuel's Paramount Theatre in July 1920; the town's first newspaper, The Peoria Enterprise, was printed weekly from November 14, 1917, to April 1921. Peoria's first library was held at the women's club in 1920 until it moved to the old Peoria City Hall in 1975; the library moved to the Peoria Municipal Complex.
In May 1959 the Women's Club gave the clubhouse to the City of Peoria. Central School was built in 1906. By 1910, three additional classroom buildings were built next to the central school, in 1918 another school building, containing an auditorium and four classrooms, was opened. In 1918 the attendance for Peoria schools was 190. School District Number Eleven was an elementary school district. Children going on to high school had to travel to Glendale High School. In 1919 the school board approved construction of Peoria High School. Increased economic activity, combined with the presence of Luke Air Force Base and tremendous growth throughout the entire Valley—coinciding with the mass-production of air conditioning in the early 1950s—led to an increase in residential housing in Peoria. A postwar construction boom set the stage for Peoria to become a suburb of Phoenix, providing housing for the capital city as growth moved west. In 1954, Peoria was home including an area of 720 acres. Peoria incorporated on June 7, 1954.
A seven-member city council formed and held its first organizational meeting on June 14. By 1966 Peoria grew to encompass 3.1 square miles with 36 miles of street. In 1968 the city passed a bond to issue securing the money to build a sewer system, completed in 1969. In 1970, Peoria began to transition to paid firefighting staff. From a population of 4,792 in 1970, the city grew to 12,351 in 1980 and 50,675 in 1990. Construction of the $30 million municipal complex began in 1988 at the edge of Peoria's Old Town; the Police Department opened in 1989, the main city hall building and courts in 1991, the library in 1993. Spring training has a long history in Peoria. From the late 1970s to 1990, Peoria's Greenway Sports Complex served as a minor-league training facility for the Milwaukee Brewers baseball team; this small facility was located at 83rd Avenue and the Greenway Road alignment, the location of the future Peoria Sports Complex. Construction of
Race and ethnicity in the United States Census
Race and ethnicity in the United States Census, defined by the federal Office of Management and Budget and the United States Census Bureau, are self-identification data items in which residents choose the race or races with which they most identify, indicate whether or not they are of Hispanic or Latino origin. The racial categories represent a social-political construct for the race or races that respondents consider themselves to be and, "generally reflect a social definition of race recognized in this country." OMB defines the concept of race as outlined for the US Census as not "scientific or anthropological" and takes into account "social and cultural characteristics as well as ancestry", using "appropriate scientific methodologies" that are not "primarily biological or genetic in reference." The race categories include both national-origin groups. Race and ethnicity are considered separate and distinct identities, with Hispanic or Latino origin asked as a separate question. Thus, in addition to their race or races, all respondents are categorized by membership in one of two ethnic categories, which are "Hispanic or Latino" and "Not Hispanic or Latino".
However, the practice of separating "race" and "ethnicity" as different categories has been criticized both by the American Anthropological Association and members of US Commission on Civil Rights. In 1997, OMB issued a Federal Register notice regarding revisions to the standards for the classification of federal data on race and ethnicity. OMB developed race and ethnic standards in order to provide "consistent data on race and ethnicity throughout the Federal Government; the development of the data standards stem in large measure from new responsibilities to enforce civil rights laws." Among the changes, OMB issued the instruction to "mark one or more races" after noting evidence of increasing numbers of interracial children and wanting to capture the diversity in a measurable way and having received requests by people who wanted to be able to acknowledge their or their children's full ancestry rather than identifying with only one group. Prior to this decision, the Census and other government data collections asked people to report only one race.
The OMB states, "many federal programs are put into effect based on the race data obtained from the decennial census. Race data are critical for the basic research behind many policy decisions. States require these data to meet legislative redistricting requirements; the data are needed to monitor compliance with the Voting Rights Act by local jurisdictions". "Data on ethnic groups are important for putting into effect a number of federal statutes. Data on Ethnic Groups are needed by local governments to run programs and meet legislative requirements." The 1790 United States Census was the first census in the history of the United States. The population of the United States was recorded as 3,929,214 as of Census Day, August 2, 1790, as mandated by Article I, Section 2 of the United States Constitution and applicable laws."The law required that every household be visited, that completed census schedules be posted in'two of the most public places within, there to remain for the inspection of all concerned...' and that'the aggregate amount of each description of persons' for every district be transmitted to the president."
This law along with U. S. marshals were responsible for governing the census. One third of the original census data has been lost or destroyed since documentation; the data was lost in 1790–1830 time period and included data from: Connecticut, Maryland, New Hampshire, New York, North Carolina, Rhode Island, South Carolina, Delaware, New Jersey, Virginia. Census data included the name of the head of the family and categorized inhabitants as follows: free white males at least 16 years of age, free white males under 16 years of age, free white females, all other free persons, slaves. Thomas Jefferson the Secretary of State, directed marshals to collect data from all thirteen states, from the Southwest Territory; the census was not conducted in Vermont until 1791, after that state's admission to the Union as the 14th state on March 4 of that year. There was some doubt surrounding the numbers, President George Washington and Thomas Jefferson maintained the population was undercounted; the potential reasons Washington and Jefferson may have thought this could be refusal to participate, poor public transportation and roads, spread out population, restraints of current technology.
No microdata from the 1790 population census is available, but aggregate data for small areas and their compatible cartographic boundary files, can be downloaded from the National Historical Geographic Information System. In 1800 and 1810, the age question regarding free white males was more detailed; the 1820
Phelps Dodge Corporation was an American mining company founded in 1834 as an import-export firm by Anson Greene Phelps and his two sons-in-law William Earle Dodge, Sr. and Daniel James. The latter two ran James & Co. the part of the organization based in Liverpool, England. The import-export firm at first exported United States cotton from the Deep South to England, imported various metals to the US needed for industrialization. With the expansion of the western frontier in North America, the corporation acquired mines and mining companies, including the Copper Queen Mine in Arizona and the Dawson, New Mexico coal mines, it acquired railroads to carry its products. By the late 19th century, it was known as a mining company. On March 19, 2007, it was acquired by Freeport-McMoRan and now operates under the name Freeport-McMoRan Copper & Gold Inc. Anson G. Phelps started a partnership in New York City during 1821 with Elisha Peck, a merchant, in trade in Berlin, Connecticut. Peck moved to Liverpool to run the British end of their business, an import-export company that shipped U.
S.-grown cotton from the Deep South to England, importing tin, iron and other metals essential for industrial growth and development in the United States. In 1834 Peck left the business and was replaced in Liverpool by Daniel James, who remained there until his death in 1876, it was at this time that the concern of Phelps Company was begun. When Anson G. Phelps died, his sons-in-law purchased his portion of the company, but retained the name, the import-export business. In 1880, the company invested in the Detroit Copper Company of Clifton, AZ, at the time a small copper camp in eastern Arizona Territory. Phelps-Dodge interested Dr. James Douglas of Phoenixville, Pennsylvania to inspect the property and make recommendations. Dr. Douglas inspected the Detroit Copper Co of Morenci and ventured south to the Warren District. On his advice, Phelps-Dodge began its own mining operations in the Warren District with the purchase of the Atlanta Copper Mine in 1882, neighboring the Copper Queen Mine; when both mines discovered the same ore body, instead of fighting over it, they merged in 1885, creating the Copper Queen Consolidated Mining Company.
The Copper Queen Mine in Bisbee, Arizona Territory, became one of the most productive in the state of the early 20th century. The company focused on providing copper wire and cables to industry, products that were in high demand as the Industrial Revolution took hold; as the company diversified, it began investing in new railroads, essential in the company’s efforts to become established in the West copper-rich Arizona. It used its own lines to transport products to and from major railroads for its markets on the eastern/northeastern shores. In 1895, the first contract was signed by Phelps Dodge and Company and the Nichols Copper Company to have Phelps Dodge deliver a minimum of 1,000,000 pounds of blister copper over three years; this economically symbiotic relationship lasted until 1922, in which Phelps Dodge provided 90% of the blister copper Nichols Copper Company used to produce 100% pure copper. During the 1920s, Phelps Dodge invested $3.5 million in the Nichols Copper Company's plant modernization projects in exchange for stock in Nichols Copper Company.
This increased copper production of the plant. In 1930, Dr. William Henry Nichols died. During the late 19th century, in concert with its metal interests, Phelps Dodge Corporation became one of the largest producers of lumber and lumber products in the United States. In Tombstone, Arizona during 1900 E. B. Gage, Frank Murphy, William Staunton consolidated their various mining properties into a single entity, the Tombstone Consolidated Mines Company, they worked to drain mines that had filled with water, laid a rail spur into town, revived mining. They experienced some success until the pumps failed in 1909; the new company filed for bankruptcy and the Phelps-Dodge Corporation acquired its claims. In 1908, with the Phelps and Dodge owners no longer alive, the company was re-organized as a public company and the name changed to Phelps Dodge Corporation, a holding company for all of the various properties and operations. Dr. Douglas was its first president; the company became notorious for its anti-union tactics for the 1917 Bisbee Deportation.
The company worked with a local group of private citizens and the county sheriff to deputize about 2,000 members of a posse. Given names of Industrial Workers of the World members and other miners, they arrested nearly 1,300 striking miners at gunpoint in Bisbee, Arizona at the Copper Queen Mine. Portraying the Wobblie miners as bent on war-related sabotage, the company ordered them expelled from the jurisdiction, deporting them to Hermanas, New Mexico. Company officials and the Sheriff seized telegraph and telephone lines to keep news of this from getting out; the Phelps Dodge copper mine at Morenci, Arizona was the site of a violent strike from 1983 to 1986, culminating in one of the largest union decertifications in American labor history. In South America, the company had several large copper mining operations in Peru. In the Congo of Africa, Phelps Dodge Corporation was the majority owner and operator of the Tenke Fungurume project considered to be the world's largest undeveloped copper/cobalt project.
A subsidiary of Phelps Dodge Corporation, Climax Molybdenum, is the largest primary producer of molybdenum in the world. At the Henderson mine west of Empire, Climax Molybdenum has produced more than 160 million tons of ore and 770 million pounds of molybdenum since the mine opened in 1
Open-pit, open-cast or open cut mining is a surface mining technique of extracting rock or minerals from the earth by their removal from an open pit or borrow. This form of mining differs from extractive methods that require tunnelling into the earth, such as long wall mining. Open-pit mines are used when deposits of commercially useful ore or rocks are found near the surface, it is applied to ore or rocks found at the surface because the overburden is thin or the material of interest is structurally unsuitable for tunnelling. In contrast, minerals that have been found underground but are difficult to retrieve due to hard rock, can be reached using a form of underground mining. To create an open-pit mine, the miners must determine the information of the ore, underground; this is done through drilling of probe holes in the ground plotting each hole location on a map. The information gained through the holes with provide an idea of the vertical extent of the ore's body; this vertical information is used to pit tentative locations of the benches that will occur in the mine.
It is important to consider the grade and economic value of the ore in the potential pit. Open-pit mines that produce building materials and dimension stone are referred to as "quarries." Open-pit mines are enlarged until either the mineral resource is exhausted, or an increasing ratio of overburden to ore makes further mining uneconomic. When this occurs, the exhausted mines are sometimes converted to landfills for disposal of solid wastes. However, some form of water control is required to keep the mine pit from becoming a lake, if the mine is situated in a climate of considerable precipitation or if any layers of the pit forming the mine border productive aquifers. Open-pit mining is to be considered one of the most dangerous sectors in the industrial world, it causes significant effects to miners health, as well as damage to the ecological land. Open-pit mining causes changes to vegetation and bedrock, which contributes to changes in surface hydrology, groundwater levels, flow paths. Additionally, open-pit produces harmful pollutants depending on the type of mineral being mined, the type of mining process being used.
Open-cast mines are dug on benches. The interval of the benches depends on the deposit being mined, the mineral being mined, the size of the machinery, being used. Large mine benches are 12 to 15 metres thick. In contrast, many quarries do not use benches, as they are shallow. Mining can be conducted on more than one bench at a time, access to different benches is done with a system of ramps; the width of each bench is determined by the size of the equipment being used 20-40 metres wide. Downward ramps are created to allow mining on a new level to begin; this new level will become progressively wider to form the new pit bottom. Most walls of the pit are mined on an angle less than vertical. Waste rock is stripped when the pit becomes deeper, therefore this angle is a safety precaution to prevent and minimize damage and danger from rock falls. However, this depends on how weathered and eroded the rocks are, the type of rocks involved, it depends on the amount of structural weaknesses occur within the rocks, such as a faults, joints or foliations.
The walls are stepped. The inclined section of the wall is known as the batter, the flat part of the step is known as the bench or berm; the steps in the walls help prevent. In some instances additional ground support is required and rock bolts, cable bolts and shotcrete are used. De-watering bores may be used to relieve water pressure by drilling horizontally into the wall, enough to cause failures in the wall by itself. A haul road is situated at the side of the pit, forming a ramp up which trucks can drive, carrying ore and waste rock. Open-pit mines create a significant amount of waste. One million tons of ore and waste rock can move from the largest mines per day, a couple thousand tons moved from small mines per day. There is four main operations in a mine that contribute to this load: drilling, blasting and hauling. Waste rock is hauled to a waste dump. Waste dumps can be piled at the surface of the active pit, or in mined pits. Leftover waste from processing the ore is called tailings, is in the form of a slurry.
This is pumped to a tailings settling pond, where the water is reused or evaporated. Tailings dams can be toxic due to the presence of unextracted sulfide minerals, some forms of toxic minerals in the gangue, cyanide, used to treat gold ore via the cyanide leach process. If proper environmental protections are not in place, this toxicity can harm the surrounding environment. Open-pit mining involves the process of disrupting the ground, which leads to the creation of air pollutants; the main source of air pollutants comes from the transportation of minerals, but their are various other factors including drilling and the loading and unloading of overburden. These type of pollutants cause significant damage to public health and safety in addition to damaging the air quality; the inhalation of these pollutants can cause issues to the lungs and increase mortality. Furthermore, the pollutants affect fauna in the areas surrounding open-pit mines. Open-pit gold mining is one of the highest potential mining threats on the environment as it affects the air and water chemistry.
The exposed dust may be toxic or radioactive, making it a health concern for the workers and the surrounding communities. A form of open-
Baghdad is the capital of Iraq. The population of Baghdad, as of 2016, is 8,765,000, making it the largest city in Iraq, the second largest city in the Arab world, the second largest city in Western Asia. Located along the Tigris River, the city was founded in the 8th century and became the capital of the Abbasid Caliphate. Within a short time of its inception, Baghdad evolved into a significant cultural and intellectual center for the Islamic world. This, in addition to housing several key academic institutions, as well as hosting multiethnic and multireligious environment, garnered the city a worldwide reputation as the "Centre of Learning". Baghdad was the largest city of the Middle Ages for much of the Abbasid era, peaking at a population of more than a million; the city was destroyed at the hands of the Mongol Empire in 1258, resulting in a decline that would linger through many centuries due to frequent plagues and multiple successive empires. With the recognition of Iraq as an independent state in 1938, Baghdad regained some of its former prominence as a significant center of Arab culture.
In contemporary times, the city has faced severe infrastructural damage, most due to the 2003 invasion of Iraq, the subsequent Iraq War that lasted until December 2011. In recent years, the city has been subjected to insurgency attacks; the war had resulted in a substantial loss of historical artifacts as well. As of 2018, Baghdad was listed as one of the least hospitable places in the world to live, ranked by Mercer as the worst of 231 major cities as measured by quality-of-life; the name Baghdad is pre-Islamic, its origin is disputed. The site where the city of Baghdad developed has been populated for millennia. By the 8th century AD, several villages had developed there, including a Persian hamlet called Baghdad, the name which would come to be used for the Abbasid metropolis. Arab authors, realizing the pre-Islamic origins of Baghdad's name looked for its roots in Persian, they suggested various meanings, the most common of, "bestowed by God". Modern scholars tend to favor this etymology, which views the word as a compound of bagh "god" and dād "given", In Old Persian the first element can be traced to boghu and is related to Slavic bog "god", while the second can be traced to dadāti.
A similar term in Middle Persian is the name Mithradāt, known in English by its Hellenistic form Mithridates, meaning "gift of Mithra". There are a number of other locations in the wider region whose names are compounds of the word bagh, including Baghlan and Bagram in Afghanistan or a village called Bagh-šan in Iran; the name of the town Baghdati in Georgia shares the same etymological origins. A few authors have suggested older origins for the name, in particular the name Bagdadu or Hudadu that existed in Old Babylonian, the Babylonian Talmudic name of a place called "Baghdatha"; some scholars suggested Aramaic derivations. When the Abbasid caliph, al-Mansur, founded a new city for his capital, he chose the name Madinat al-Salaam or City of Peace; this was the official name on coins and other official usage, although the common people continued to use the old name. By the 11th century, "Baghdad" became the exclusive name for the world-renowned metropolis. After the fall of the Umayyads, the first Muslim dynasty, the victorious Abbasid rulers wanted their own capital from which they could rule.
They chose a site north of the Sassanid capital of Ctesiphon, on 30 July 762 the caliph Al-Mansur commissioned the construction of the city. It was built under the supervision of the Barmakids. Mansur believed that Baghdad was the perfect city to be the capital of the Islamic empire under the Abbasids. Mansur loved the site so much he is quoted saying: "This is indeed the city that I am to found, where I am to live, where my descendants will reign afterward"; the city's growth was helped by its excellent location, based on at least two factors: it had control over strategic and trading routes along the Tigris, it had an abundance of water in a dry climate. Water exists on both the north and south ends of the city, allowing all households to have a plentiful supply, uncommon during this time. Baghdad eclipsed Ctesiphon, the capital of the Sassanians, located some 30 km to the southeast. Today, all that remains of Ctesiphon is the shrine town of Salman Pak, just to the south of Greater Baghdad.
Ctesiphon itself had replaced and absorbed Seleucia, the first capital of the Seleucid Empire, which had earlier replaced the city of Babylon. According to the traveler Ibn Battuta, Baghdad was one of the largest cities, not including the damage it has received; the residents are Hanbal. Bagdad is home to the grave of Abu Hanifa where there is a cell and a mosque above it; the Sultan of Bagdad, Abu Said Bahadur Khan, was a Tartar king. In its early years, the city was known as a deliberate reminder of an expression in the Qur'an, when it refers to Paradise, it took four years to build. Mansur assembled engineers and art constructionists from around the world to come together and draw up plans for the city. Over 100,000 construction workers came to survey the plans. July was chosen as the starting time because two astrologers, Naubakht Ahva
Copper extraction refers to the methods used to obtaining copper from its ores. The conversion of copper consists of a series of electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, other factors; as in all mining operations, the ore must be beneficiated. The processing techniques depend on the nature of the ore. If the ore is sulfide copper minerals, the ore is crushed and ground to liberate the valuable minerals from the waste minerals, it is concentrated using mineral flotation. The concentrate is then sold to distant smelters, although some large mines have smelters located nearby; such colocation of mines and smelters was more typical in the 19th and early 20th centuries, when smaller smelters could be economic. The sulfide concentrates are smelted in such furnaces as the Outokumpo or Inco flash furnace or the ISASMELT furnace to produce matte, which must be converted and refined to produce anode copper; the final refining process is electrolysis.
For economic and environmental reasons, many of the byproducts of extraction are reclaimed. Sulfur dioxide gas, for example, is captured and turned into sulfuric acid — which can be used in the extraction process or sold for such purposes as fertiliser manufacture. Oxidised copper ores can be treated by hydrometallurgical extraction; the earliest evidence of cold-hammering of native copper comes from the excavation at Çaÿonü Tepesi in eastern Anatolia, which dates between 7200 to 6600 BCE. Among the various items considered to be votive or amulets there was one that looked like a fishhook and one like an awl. Another find, at Shanidar Cave in Mergasur, contained copper beads, dates to 8,700 BCE; the world's oldest known copper mine, as opposed to usage of surface deposits, is at Timna Valley, since the fourth millennium BC, with smelting and surface deposit usage since the sixth to fifth millennium. Pločnik archaeological site in southeastern Europe contains the oldest securely dated evidence of copper making at high temperature, from 5,000 BCE.
The find in June 2010 extends for additional 500 years the earlier record of copper smelting from Rudna Glava, dated to 5th millennium BCE. Copper smelting technology gave rise to the Copper Age, aka Chalcolithic Age, the Bronze Age; the Bronze Age would not have been possible without humans developing smelting technology. Most copper ores contain only a small percentage of copper metal bound up within valuable ore minerals, with the remainder of the ore being unwanted rock or gangue minerals silicate minerals or oxide minerals for which there is no value. In some cases, tailings have been retreated to recover lost value as the technology for recovering copper has improved; the average grade of copper ores in the 21st century is below 0.6% copper, with a proportion of economic ore minerals being less than 2% of the total volume of the ore rock. A key objective in the metallurgical treatment of any ore is the separation of ore minerals from gangue minerals within the rock; the first stage of any process within a metallurgical treatment circuit is accurate grinding or comminution, where the rock is crushed to produce small particles consisting of individual mineral phases.
These particles are separated to remove gangue, thereafter followed by a process of physical liberation of the ore minerals from the rock. The process of liberation of copper ores depends upon whether they are sulfide ores. Subsequent steps depend on the nature of the ore containing the copper. For oxide ores, a hydrometallurgical liberation process is undertaken, which uses the soluble nature of the ore minerals to the advantage of the metallurgical treatment plant. For sulfide ores, both secondary and primary, froth flotation is used to physically separate ore from gangue. For special native copper bearing ore bodies or sections of ore bodies rich in supergene native copper, this mineral can be recovered by a simple gravity circuit; the modern froth flotation process was independently invented the early 1900s in Australia by C. V Potter and around the same time by G. D. Delprat. All primary sulfide ores of copper sulfides, most concentrates of secondary copper sulfides, are subjected to smelting.
Some vat leach or pressure leach processes exist to solubilise chalcocite concentrates and produce copper cathode from the resulting leachate solution, but this is a minor part of the market. Carbonate concentrates are a minor product produced from copper cementation plants as the end-stage of a heap-leach operation; such carbonate concentrates can be treated by a solvent extraction and electrowinning plant or smelted. The copper ore is crushed and ground to a size such that an acceptably high degree of liberation has occurred between the copper sulfide ore minerals and the gangue minerals; the ore is wet, suspended in a slurry, mixed with xanthates or other reagents, which render the sulfide particles hydrophobic. Typical reagents include potassium ethylxanthate and sodium ethylxanthate, but dithiophosphates and dithiocarbamates are used; the treated ore is introduced to a water-filled aeration tank containing surfactant such as methylisobutyl carbinol. Air is forced through the slurry and the air bubbles attach to the hydrophobic copper sulfide particles, which are conducted to the surface, where they form a froth and are skimmed off.
These skimmings are subjected to a cleaner-scavenger cell to remove excess silicates and to remove other sulfide minerals that can deleteriousl