Springbok is the administrative and commercial centre of Namaqualand and lies in a narrow valley surrounded by the Koperberge (copper mountains). It was established in 1862 after mining began in the area nearly two centuries after the mineral was first discovered here. In 1685 an expedition led by Simon van der Stel sank a shaft and discovered copper near Springbok. This shaft is now a national monument together with the old smelting furnace built by the Cape Copper Mining Company in 1866. The Blue Mine is recorded as the first commercial mining endeavour in South Africa, and started operations in the mid-nineteenth century (1852-1862). The mineral involved was copper, which was primarily the driving force behind the establishing of Springbok, Okiep and Nababeep as formal towns. The blue tinge of the rocks in the mine is a result of copper coming into contact with oxygen in the air. Nearly two centuries has lapsed since the first discovery of copper in the area by Simon van der Stel, Governer of the Cape, at Carolusberg in 1685.

In the late 1870s rich copper deposits were discovered to the north at Okiep and people flocked to the scene of the new discovery, but because the spring at Springbok was the nearest supply of drinkable water, the town became a centre for mining prospectors. The Blue Mine, on the western outskirts of Springbok, provides an excellent view of the town. The Anglican Church, built in 1861, houses the Tourism Information Office while the Synagogue, completed in 1929, houses the Namaqualand Museum. The Springbok Lodge has permanent photographic, mineral and semiprecious stone displays which are of great interest. The photographic collection captures Namaqualand's kaleidoscope of striking scenery and intriguing history.

Of historical interest is Monument Koppie, a hill in the centre of Springbok surrounded by Anglo-Boer War monuments. Springbok is a centre for tourists who come to view the spring wild flowers and other attractions in the area. Set in a narrow valley bisecting the granite domes of the Klein Koperberge (small copper mountains), is the principal town of Namakwa, Springbok. Shortened from Springbokfontein in 1911, it owes its existence to copper-mining undertaken after 1850 and a ready supply of water.

In the late 1870s, rich copper deposits at Okiep saw most Springbok residents following their dreams to drought-stricken claims. Many returned.

Mining and Refining of Copper

From the mines, copper ore is taken to mills, where it is crushed and finely ground in preparation for refining. The method of refining varies with the type of ore.

In the case of copper-oxide ores, the copper is usually leached (dissolved) from the ore with a solution of sulfuric acid.

The copper can be recovered from the leaching solution through electrolysis. In this process, a direct electric current is set up between positive and negative electrodes placed in the solution. The negative electrodes, called cathodes, are usually made of thin sheets of pure copper and the positive electrodes, called anodes, are usually made of lead. The electric current causes the copper in the solution to be deposited on the cathodes as a coating of pure copper.

Another method is to pass the solution over scrap iron; a chemical reaction causes the copper to be deposited on the iron. The copper is separated from the iron by methods used to refine copper-sulfide ores (many of which also contain iron).

Copper-sulfide ores are first treated by a process called flotation. In this process, bubbles are produced in a mixture of ground copper ore, water, and chemical reagents. The particles of copper-bearing minerals in the ore stick to the bubbles and float to the top of the mixture, where they can be skimmed off.

The copper-bearing minerals are roasted to drive off a part of the sulfur. The resulting product is smelted, yielding a molten combination of copper sulfate and iron sulfide called matte. Some light impurities in the matte combine to form slag, which is removed. The matte is then poured into a converter, where air is forced through it to burn out the remaining sulfur and to oxidize the iron. At this stage, most of the remaining impurities, including the oxidized iron, float to the top of the matte to form more slag, which is poured off.

The metallic copper that is left at the bottom of the converter is known as blister copper. It is very pure, but further refining is necessary to remove impurities consisting of small amounts of gold, silver, and other precious metals.

This refining is done electrochemically, using a process similar to the one used with oxide ores. In this case, however, the anode is molded from blister copper and decomposes during electrolysis. The direct electric current that flows between the electrodes placed in an electrolytic tank transfers the copper of the blister copper anode onto the cathode. The precious-metal impurities collect at the bottom of the tank.

A significant portion of the copper produced today is refined from copper scrap. Copper produced from scrap is called secondary copper.

Copper extraction techniques

Copper extraction techniques refers to the methods for obtaining copper from its ores. This conversion consists of a series of chemical, physical, and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors.

As in all mining operations, the ore must usually be beneficiated (concentrated). To do this, the ore is crushed. Then it must be roasted to convert sulfides to oxides, which are smelted to produce matte. Finally, it undergoes various refining processes, the final one being 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 is then used in the extraction process.

History

The earliest evidence of cold-hammering of native copper comes from the excavation at Çaÿonü Tepesi in eastern Anatolia. The radiocarbon date is 7250 ± 250 BCE. Among the various items considered to be votive or amulets there was one that looked like a fishhook and one like an awl.

An archaeological site in southeastern Europe (Serbia) contains the oldest securely dated evidence of copper making at high temperature, from 7,000 years ago. The find in June 2010 extends the known record of copper smelting by about 500 years, and suggests that copper smelting may have been invented in separate parts of Asia and Europe at that time rather than spreading from a single source.

Copper smelting technology gave rise to the Copper Age and then the Bronze Age.

Concentration

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 (<100 μm) consisting of individual mineral phases. These particles are then 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 oxide or sulfide ores.

Subsequent steps depend on the nature of the ore containing the copper. For oxide ores, a hydrometallurgical liberation process is normally undertaken, which uses the soluble nature of the ore minerals to the advantage of the metallurgical treatment plant. For sulfide ores, both secondary (supergene) and primary (unweathered), froth flotation is used to physically separate ore from gangue. For special native copper bearing ore bodies or sections of ore bodies rich in supergen native copper, this mineral can be recovered by a simple gravity circuit.

1. Hydrometallurgical extraction

1.1 Sulfide ores

Supergene ores rich in sulfides may be concentrated using froth flotation. A typical concentrate of chalcocite can grade between 37% and 40% copper in sulfide, making them relatively cheap to smelt compared to chalcopyrite concentrates.

Some supergene sulfide deposits can be leached using a bacterial oxidation heap leach process to oxidize the sulfides to sulfuric acid, which also allows for simultaneous leaching with sulfuric acid to produce a copper sulfate solution. As with oxide ores, solvent extraction and electrowinning technologies are used to recover the copper from the pregnant leach solution.

Supergene sulfide ores rich in native copper minerals are refractory to treatment with sulfuric acid leaching on all practicable time scales, and the dense metal particles do not react with froth flotation media. Typically, if native copper is a minor part of a supergene profile it will not be recovered and will report to the tailings. When rich enough, native copper ore bodies may be treated to recover the contained copper via a gravity separation circuit where the density of the metal is used to liberate it from the lighter silicate minerals. Often, the nature of the gangue is important, as clay-rich native copper ores prove difficult to liberate.

1.2 Oxide ores

Oxidised copper ore bodies may be treated via several processes, with hydrometallurgical processes used to treat oxide ores dominated by copper carbonate minerals such as azurite and malachite, and other soluble minerals such as silicates like chrysocolla, or sulfates such as atacamite and so on.

Such oxide ores are usually leached by sulfuric acid, usually in a heap leaching or dump leaching process to liberate the copper minerals into a solution of sulfuric acid laden with copper sulfate in solution. The copper sulfate solution (the pregnant leach solution) is then stripped of copper via a solvent extraction and electrowinning (SX-EW) plant, with the barred (denuded) sulfuric acid recycled back on to the heaps. Alternatively, the copper can be precipitated out of the pregnant solution by contacting it with scrap iron; a process called cementation. Cement copper is normally less pure than SX-EW copper. Commonly sulfuric acid is used as a leachant for copper oxide, although it is possible to use water, particularly for ores rich in ultra-soluble sulfate minerals.

^{In general, froth flotation is not used to concentrate copper oxide ores, as oxide minerals are not responsive to the froth flotation chemicals or process (i.e.; they do not bind to the kerosene-based chemicals). Copper oxide ores have occasionally been treated via froth flotation via sulfidation of the oxide minerals with certain chemicals which react with the oxide mineral particles to produce a thin rime of sulfide (usually chalcocite), which can then be activated by the froth flotation plant.}

^{2. Sulfide smelting}

2.1 Froth flotation

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All primary sulfide ores of copper sulfides, and most concentrates of secondary copper sulfides (being chalcocite), are subjected to smelting. Some vat leach or processes exist to pressure leachsolubilise chalcocite concentrates and produce copper cathode from the resulting leachate solution, but this is a minor part of the market.

Carbonate concentrates are a relatively minor product produced from copper cementation plants, typically as the end-stage of a heap-leach operation. Such carbonate concentrates can be treated by a SX-EW 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 then wet, suspended in a slurry, and 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 also used.

The treated ore is introduced to a water-filled aeration tank containing surfactant such as methylisobutyl carbinol (MIBC). Air is constantly 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 generally subjected to a cleaner-scavenger cell to remove excess silicates and to remove other sulfide minerals that can deleteriously impact the concentrate quality (typically, galena), and the final concentrate sent for smelting. The rock which has not floated off in the flotation cell is either discarded as tailings or further processed to extract other metals such as lead (from galena) and zinc (from sphalerite), should they exist. To improve the process efficiency, lime is used to raise the pH of the water bath, causing the collector to ionize more and to preferentially bond to chalcopyrite (CuFeS₂) and avoid the pyrite (FeS₂). Iron exists in both primary zone minerals. Copper ores containing chalcopyrite can be concentrated to produce a concentrate with between 20% and 30% copper-in-concentrate (usually 27–29% copper); the remainder of the concentrate is iron and sulfur in the chalcopyrite, and unwanted impurities such as silicate gangue minerals or other sulfide minerals, typically minor amounts of pyrite, sphalerite or galena. Chalcocite concentrates typically grade between 37% and 40% copper-in-concentrate, as chalcocite has no iron within the mineral.

2.2 Roasting

As of 2005, roasting is no longer common in copper concentrate treatment. Direct smelting is now favored, e.g. using the following smelting technologies: ISASMELT^TM, flash smelting, Noranda, Top-entry Submerged Lance, Mitsubishi or El Teniente furnaces.

2.3 Smelting

The calcine is then mixed with silica and coke and smelted in an exothermic reaction at 1200 °C (above the melting point of copper, but below that of the iron and silica) to form a liquid called "copper matte". The high temperature allows reactions to proceed rapidly, and allow the matte and slag to melt, so they can be "tapped out" of the furnace. In copper recycling, this is the point where scrap copper is introduced.

The slag is discarded or reprocessed to recover any remaining copper. The sulphuric acid is captured for use in earlier leaching processes.

2.4 Converting

In a parallel reaction the iron sulfide is converted to slag:

The purity of this product is 98%, it is known as blister because of the broken surface created by the escape of sulfur dioxide gas as blister copper pigs or ingots are cooled. By-products generated in the process are sulfur dioxide and slag. The sulfur dioxide is captured for use in earlier leaching processes.

2.5 Fire refining

The blistered copper is put into an anode furnace (a furnace that uses the blister copper as anode) to get rid of most of the remaining oxygen. This is done by blowing natural gas through the molten copper oxide. When this flame burns green, indicating the copper oxidation spectrum, the oxygen has mostly been burned off. This creates copper at about 99% pure. The anodes produced from this are fed to the electrorefinery.

2.6 Electrorefining

The copper is refined by electrolysis. The anodes cast from processed blister copper are placed into an aqueous solution of 3–4% copper sulfate and 10–16% sulfuric acid. Cathodes are thin rolled sheets of highly pure copper. A potential of only 0.2–0.4 volts is required for the process to commence. At the anode, copper and less noble metals dissolve. More noble metals such as silver and gold as well as selenium and tellurium settle to the bottom of the cell as anode slime, which forms a saleable byproduct. Copper(II) ions migrate through the electrolyte to the cathode. At the cathode, copper metal plates out but less noble constituents such as arsenic and zinc remain in solution. The reactions are:

At the anode: Cu_(s) → Cu²⁺_(aq) + 2e^–

At the cathode: Cu²⁺_(aq) + 2e^– → Cu_(s)

Amongst other things copper is used for:

• ^{electrical wiring. It is a very good conductor of electricity and is easily drawn out into wires. .}

• ^{domestic plumbing. It doesn't react with water, and is easily bent into shape.}

• ^{boilers and heat exchangers. It is a good conductor of heat and doesn't react with water.}

• ^{making brass. Brass is a copper-zinc alloy. Alloying produces a metal harder than either copper or zinc individually. Bronze is another copper alloy - this time with tin.}

• ^{coinage. In the UK, as well as the more obvious copper-coloured coins, "silver" coins are also copper alloys - this time with nickel. These are known as cupronickel alloys. UK pound coins and the gold-coloured bits of euro coins are copper-zinc-nickel alloys.}

^{To qualify, please answer the following questions:}

^{1. What is the general colour of the stones in this quarry and why?}

^{2. When was copper economically mined here and by which company. Who is the current owners of this mine?}

^{3. What type of mining technique were used here?}

^{4. In your own words, describe one refining method?}

^{5. Find interresting coloured stones and describe the appearance and optionally post potographs with your log.}

^{6. OPTIONAL: Please take photograph of yourself/team at the plaque. PLEASE do not post photographs of the plaque in your log as answer to question 2 are found there.}