Mining is the extraction of valuable minerals or other geological materials from the earth from an ore body, vein, reef or placer deposit. These deposits form a mineralized package, of economic interest to the miner. Ores recovered by mining include metals, oil shale, limestone, dimension stone, rock salt, potash and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, or feasibly created artificially in a laboratory or factory. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or water. Mining of stones and metal has been a human activity since pre-historic times. Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, final reclamation of the land after the mine is closed. De Re Metallica, Georgius Agricola, 1550, Book I, Para. 1Mining operations create a negative environmental impact, both during the mining activity and after the mine has closed.
Hence, most of the world's nations have passed regulations to decrease the impact. Work safety has long been a concern as well, modern practices have improved safety in mines. Levels of metals recycling are low. Unless future end-of-life recycling rates are stepped up, some rare metals may become unavailable for use in a variety of consumer products. Due to the low recycling rates, some landfills now contain higher concentrations of metal than mines themselves. Since the beginning of civilization, people have used stone and metals found close to the Earth's surface; these were used to make early weapons. Flint mines have been found in chalk areas where seams of the stone were followed underground by shafts and galleries; the mines at Grimes Graves and Krzemionki are famous, like most other flint mines, are Neolithic in origin. Other hard rocks mined or collected for axes included the greenstone of the Langdale axe industry based in the English Lake District; the oldest-known mine on archaeological record is the Ngwenya Mine in Swaziland, which radiocarbon dating shows to be about 43,000 years old.
At this site Paleolithic humans mined hematite to make the red pigment ochre. Mines of a similar age in Hungary are believed to be sites where Neanderthals may have mined flint for weapons and tools. Ancient Egyptians mined malachite at Maadi. At first, Egyptians used the bright green malachite stones for ornamentations and pottery. Between 2613 and 2494 BC, large building projects required expeditions abroad to the area of Wadi Maghareh in order to secure minerals and other resources not available in Egypt itself. Quarries for turquoise and copper were found at Wadi Hammamat, Tura and various other Nubian sites on the Sinai Peninsula and at Timna. Mining in Egypt occurred in the earliest dynasties; the gold mines of Nubia were among the largest and most extensive of any in Ancient Egypt. These mines are described by the Greek author Diodorus Siculus, who mentions fire-setting as one method used to break down the hard rock holding the gold. One of the complexes is shown in one of the earliest known maps.
The miners crushed the ore and ground it to a fine powder before washing the powder for the gold dust. Mining in Europe has a long history. Examples include the silver mines of Laurium. Although they had over 20,000 slaves working them, their technology was identical to their Bronze Age predecessors. At other mines, such as on the island of Thassos, marble was quarried by the Parians after they arrived in the 7th century BC; the marble was shipped away and was found by archaeologists to have been used in buildings including the tomb of Amphipolis. Philip II of Macedon, the father of Alexander the Great, captured the gold mines of Mount Pangeo in 357 BC to fund his military campaigns, he captured gold mines in Thrace for minting coinage producing 26 tons per year. However, it was the Romans who developed large scale mining methods the use of large volumes of water brought to the minehead by numerous aqueducts; the water was used for a variety of purposes, including removing overburden and rock debris, called hydraulic mining, as well as washing comminuted, or crushed and driving simple machinery.
The Romans used hydraulic mining methods on a large scale to prospect for the veins of ore a now-obsolete form of mining known as hushing. They built numerous aqueducts to supply water to the minehead. There, the water stored in large tanks; when a full tank was opened, the flood of water sluiced away the overburden to expose the bedrock underneath and any gold veins. The rock was worked upon by fire-setting to heat the rock, which would be quenched with a stream of water; the resulting thermal shock cracked the rock, enabling it to be removed by further streams of water from the overhead tanks. The Roman miners used similar methods to work cassiterite deposits in Cornwall and lead ore in the Pennines; the methods had been developed by the Romans in Spain in 25 AD to exploit large alluvial gold deposits, the largest site being at Las Medulas, where seven long aqueducts tapped local rivers and sluiced the deposits. Spain was one of the most important mining regions, but all regions of the Roman Empire were exploited.
In Great Britain the natives had mined minerals for millennia, but after the Roman conquest, the scale of the operations increased as the Romans needed Britannia's resources gold, silver
Bougainville Island is the main island of the Autonomous Region of Bougainville of Papua New Guinea. This region is known as Bougainville Province or the North Solomons, its land area is 9,300 km2. The population of the province is 234,280, which includes the adjacent island of Buka and assorted outlying islands including the Carterets. Mount Balbi at 2,700 m is the highest point. Bougainville Island is the largest of the Solomon Islands archipelago, forming part of the Northern Solomon Islands, politically separate from the sovereign country called Solomon Islands. Bougainville was first settled some 28,000 years ago. Three to four thousand years ago, Austronesian people arrived, bringing with them domesticated pigs, chickens and obsidian tools; the first European contact with Bougainville was in 1768, when the French explorer Louis de Bougainville arrived and named the main island for himself. Germany laid claim to Bougainville in 1899. Christian missionaries arrived on the island in 1902. During World War I, Australia occupied German New Guinea, including Bougainville.
It became part of the Australian Territory of New Guinea under a League of Nations mandate in 1920. In 1942, during World War II, Japan invaded the island, but allied forces launched the Bougainville campaign to regain control of the island in 1943. Despite heavy bombardments, the Japanese garrisons remained on the island until 1945. Following the war, the Territory of New Guinea, including Bougainville, returned to Australian control. In 1949, the Territory of New Guinea, including Bougainville, merged with the Australian Territory of Papua, forming the Territory of Papua and New Guinea, a United Nations Trust Territory under Australian administration. On 9 September 1975, the Parliament of Australia passed the Papua New Guinea Independence Act 1975; the Act set 16 September 1975 as date of independence and terminated all remaining sovereign and legislative powers of Australia over the territory. Bougainville was to become part of an independent Papua New Guinea. However, on 11 September 1975, in a failed bid for self-determination, Bougainville declared itself the Republic of the North Solomons.
The republic failed to achieve any international recognition, a settlement was reached in August 1976. Bougainville was absorbed politically into Papua New Guinea with increased self-governance powers. Between 1988 and 1998, the Bougainville Civil War claimed over 15,000 lives. Peace talks brokered by New Zealand led to autonomy. A multinational Peace Monitoring Group under Australian leadership was deployed. In 2001, a peace agreement was signed including promise of a referendum on independence from Papua New Guinea, which will be held in 2019. Bougainville is the largest island in the Solomon Islands archipelago, it is part of the Solomon Islands rain forests ecoregion. Bougainville and the nearby island of Buka are a single landmass separated by a deep 300-metre-wide strait; the island has an area of 9000 square kilometres, there are several active, dormant or inactive volcanoes which rise to 2400 m. Mount Bagana in the north central part of Bougainville is conspicuously active, spewing out smoke, visible many kilometres distant.
Earthquakes cause little damage. The daily volume of wild rivers appears to be decreasing; this has been affected by deforestation caused by the increased demand for gardens to feed the growing population. Mining with its use of chemicals and its aftereffects poses other environmental issues, e.g. alluvial gold mining and the now decommissioned Rio Tinto-owned Panguna mine. Bougainville has one of the world's largest copper deposits; these have been under development since 1972. The majority of people on Bougainville are Christian, an estimated 70% being Roman Catholic and a substantial minority United Church of Papua New Guinea since 1968. Few non-natives remain. There are many indigenous languages in Bougainville Province, belonging to three language families; the languages of the northern end of the island, some scattered around the coast, belong to the Austronesian family. The languages of the north-central and southern lobes of Bougainville Island belong to the North and South Bougainville families.
The most spoken Austronesian language is Halia and its dialects, spoken in the island of Buka and the Selau peninsula of Northern Bougainville. Other Austronesian languages include Nehan, Solos, Saposa and Tinputz, all spoken in the northern quarter of Bougainville and surrounding islands; these languages are related. Bannoni and Torau are Austronesian languages not related to the former, which are spoken in the coastal areas of central and south Bougainville. On the nearby Takuu Atoll a Polynesian language is spoken, Takuu; the Papuan languages are confined to the main island of Bougainville. These include Rotokas, a language with a small inventory of phonemes, Terei, Nasioi, Siwai, Baitsi and several others; these constitute North Bougainville and South Bougainville. None of the languages are spoken by more than 20% of the population, the larger languages such as Nasioi, Korokoro Motuna and Halia are split into dialects that are not always mutually understandable. For general communication most Bougainvilleans use Tok Pisin as a lingua franca, at least in the coastal areas Tok Pisin is learned by children in a bilingual environment.
English and Tok Pisin are the languages of official government. A 2013 U
Tasmania is an island state of Australia. It is located 240 km to the south of the Australian mainland, separated by Bass Strait; the state encompasses the main island of Tasmania, the 26th-largest island in the world, the surrounding 334 islands. The state has a population of around 526,700 as of March 2018. Just over forty percent of the population resides in the Greater Hobart precinct, which forms the metropolitan area of the state capital and largest city, Hobart. Tasmania's area is 68,401 km2, of which the main island covers 64,519 km2, it is promoted as a natural state, protected areas of Tasmania cover about 42% of its land area, which includes national parks and World Heritage Sites. Tasmania was the founding place of the first environmental political party in the world; the island is believed to have been occupied by indigenous peoples for 30,000 years before British colonisation. It is thought Aboriginal Tasmanians were separated from the mainland Aboriginal groups about 10,000 years ago when the sea rose to form Bass Strait.
The Aboriginal population is estimated to have been between 3,000 and 7,000 at the time of colonisation, but was wiped out within 30 years by a combination of violent guerrilla conflict with settlers known as the "Black War", intertribal conflict, from the late 1820s, the spread of infectious diseases to which they had no immunity. The conflict, which peaked between 1825 and 1831, led to more than three years of martial law, cost the lives of 1,100 Aboriginals and settlers; the island was permanently settled by Europeans in 1803 as a penal settlement of the British Empire to prevent claims to the land by the First French Empire during the Napoleonic Wars. The island was part of the Colony of New South Wales but became a separate, self-governing colony under the name Van Diemen's Land in 1825. 75,000 convicts were sent to Van Diemen's Land before transportation ceased in 1853. In 1854 the present Constitution of Tasmania was passed, the following year the colony received permission to change its name to Tasmania.
In 1901 it became a state through the process of the Federation of Australia. The state is named after Dutch explorer Abel Tasman, who made the first reported European sighting of the island on 24 November 1642. Tasman named the island Anthony van Diemen's Land after his sponsor Anthony van Diemen, the Governor of the Dutch East Indies; the name was shortened to Van Diemen's Land by the British. It was renamed Tasmania in honour of its first European discoverer on 1 January 1856. Tasmania was sometimes referred to as "Dervon," as mentioned in the Jerilderie Letter written by the notorious Australian bushranger Ned Kelly in 1879; the colloquial expression for the state is "Tassie". Tasmania is colloquially shortened to "Tas," when used in business names and website addresses. TAS is the Australia Post abbreviation for the state; the reconstructed Palawa kani language name for Tasmania is Lutriwita. The island was adjoined to the mainland of Australia until the end of the last glacial period about 10,000 years ago.
Much of the island is composed of Jurassic dolerite intrusions through other rock types, sometimes forming large columnar joints. Tasmania has the world's largest areas of dolerite, with many distinctive mountains and cliffs formed from this rock type; the central plateau and the southeast portions of the island are dolerites. Mount Wellington above Hobart is a good example. In the southern midlands as far south as Hobart, the dolerite is underlaid by sandstone and similar sedimentary stones. In the southwest, Precambrian quartzites were formed from ancient sea sediments and form strikingly sharp ridges and ranges, such as Federation Peak or Frenchmans Cap. In the northeast and east, continental granites can be seen, such as at Freycinet, similar to coastal granites on mainland Australia. In the northwest and west, mineral-rich volcanic rock can be seen at Mount Read near Rosebery, or at Mount Lyell near Queenstown. Present in the south and northwest is limestone with caves; the quartzite and dolerite areas in the higher mountains show evidence of glaciation, much of Australia's glaciated landscape is found on the Central Plateau and the Southwest.
Cradle Mountain, another dolerite peak, for example, was a nunatak. The combination of these different rock types contributes to scenery, distinct from any other region of the world. In the far southwest corner of the state, the geology is wholly quartzite, which gives the mountains the false impression of having snow-capped peaks year round. Evidence indicates the presence of Aborigines in Tasmania about 42,000 years ago. Rising sea levels cut Tasmania off from mainland Australia about 10,000 years ago and by the time of European contact, the Aboriginal people in Tasmania had nine major nations or ethnic groups. At the time of the British occupation and colonisation in 1803, the indigenous population was estimated at between 3,000 and 10,000. Historian Lyndall Ryan's analysis of population studies led her to conclude that there were about 7,000 spread throughout the island's nine nations. J. B. Plomley and Rhys Jones, settled on a figure of 3,000 to 4,000, they engaged in fire-stick farming, hunted game including kangaroo and wallabies, caught seals, mutton-birds and fish and lived as nine separate "nations" on the island, which they knew as "Trouwunna".
The first reported sighting of Tasmania by a European was on 24 November 1642 by Dutch explorer Abel Tasman, who landed at today's Blackman Bay. More than a century in 1772, a French expedition le
Stoping is the process of extracting the desired ore or other mineral from an underground mine, leaving behind an open space known as a stope. Stoping is used when the country rock is sufficiently strong not to collapse into the stope, although in most cases artificial support is provided; the earliest forms of stoping were conducted by fire-setting. From the 19th century onward, various other explosives, power-tools, machines came into use; as mining progresses the stope is backfilled with tailings, or when needed for strength, a mixture of tailings and cement. In old mines, stopes collapse at a time, leaving craters at the surface, they are an unexpected danger when records of underground mining have been lost with the passage of time. Stoping is considered "productive work", is contrasted with "deadwork", the work required to access the mineral deposit, such as sinking shafts and winzes, carving adits and levels, establishing ventilation and transportation. A stope can be created in a variety of ways.
The specific method of stoping depends on a number of considerations, both technical and economical, based on the geology of the ore body being mined. These include the incline of the deposit, the width of the deposit, the grade of the ore, the hardness and strength of the surrounding rock, the cost of materials for supports, it is common to dig shafts vertically downwards to reach the ore body and drive horizontal levels through it. Stoping takes place from these levels; when the ore body is more or less horizontal, various forms of room and pillar stoping and fill, or longwall mining can take place. In steeply-dipping ore bodies, such as lodes of tin, the stopes become long narrow near-vertical spaces, which, if one reaches the surface is known as a gunnis or coffen. A common method of mining such vertical ore bodies is stull stoping. Open stoping is divided into two basic forms based on direction: overhand and underhand stoping, which refer to the removal of ore from above or below the level, respectively.
It is possible to combine the two in a single operation. Underhand stoping known as horizontal-cut underhand or underbreaking stoping, is the working of an ore deposit from the top downwards. Like shrinkage stoping, underhand stoping is most suitable for steeply dipping ore bodies; because of the mechanical advantage it offers hand tools being struck downward, this method was dominant prior to the invention of rock blasting and powered tools. In overhand stoping, the deposit is worked from the bottom upward, the reverse of underhand stoping. With the advent of rock blasting and power drills, it became the predominant direction of stoping. In combined stoping, the deposit is worked from the bottom upward and the top downward, combining the techniques of overhand and underhand stoping into a single approach. Breast stoping is a method used in horizontal or near-horizontal ore bodies, where gravity is not usable to move the ore around. Breast stoping lacks the characteristic "steps" of either underhand or overhand stoping, being mined in a singular cut.
Room and pillar is a type of breast stoping. Stull stoping is a form of stoping used in hardrock mining that uses systematic or random timbering placed between the foot and hanging wall of the vein; the method requires that the hanging wall and the footwall be of competent rock as the stulls provide the only artificial support. This type of stope has been used up at intervals up to 12 feet wide; the 1893 mining disaster at Dolcoath mine in Cornwall was caused by failure of the stulls holding up a huge weight of waste rock. Square-set stoping is a method relying on square-set timbering. Square set timbers are set into place as support and are filled with cement; the cement uses fine tailings. This is a specialized method of stoping requiring expert input. Square set was invented in the Comstock Lode, Virginia City, Nevada in the 1860s, they utilized the waste rock to fill the stopes. Shrinkage stoping, is most suitable for steeply dipping ore bodies. In shrinkage stoping, mining proceeds from the bottom upwards, in horizontal slices, with the broken ore being left in place for miners to work from.
Because blasted rock takes up a greater volume than in situ rock, some of the blasted ore must be removed to provide working space for the next ore slice. Once the top of the stope is reached all the ore is removed from the stope; the stope may be left empty, depending on the rock conditions. Long hole stoping as the name suggests uses holes drilled by a production drill to a predetermined pattern as designed by a Mining Engineer. Long hole stoping is a selective and productive method of mining and can cater for varying ore thicknesses and dips, it differs from manual methods such as timbered and shrinkage as once the stope has begun blasting phase it cannot be accessed by personnel. For this reason the blasted rock is designed to fall into a supported drawpoint or removed with remote control LHD; the biggest limitation with this method is the length of holes that can be drilled by the production drill, larger diameter holes using in the hole hammer drills can be accurate to over 100 m in length while floating boom top hammer rigs are limited to ~30 m.
Holes drilled underground are drilled perpendicular, in a radial pattern around the drive. For the blastholes to extract the ore material they must be able to fire into a v
Bauxite tailings known as red mud, red sludge, bauxite residue, or alumina refinery residues, is a alkaline waste product composed of iron oxide, generated in the industrial production of alumina. Annually, about 77 million tons of the red special waste are produced, causing a serious disposal problem in the mining industry; the scale of production makes the waste product an important one, issues with its storage are reviewed and every opportunity is explored to find uses for it. Over 95% of the alumina produced globally is through the Bayer process. Annual production of alumina in 2015 was 115 million tonnes resulting in the generation of about 150 million tonnes of bauxite tailings/residue. Red mud is a side-product of the Bayer process, the principal means of refining bauxite en route to alumina; the resulting alumina is the raw material for producing aluminium by the Hall–Héroult process. A typical bauxite plant produces one to two times as much red mud as alumina; this ratio is dependent on the type of bauxite used in the refining process and the extraction conditions.
There are over 60 manufacturing operations across the world using the Bayer process to make alumina from bauxite ore. Bauxite ore is mined in open cast mines, transferred to an alumina refinery for processing; the alumina is extracted using sodium hydroxide under conditions of high pressure. The insoluble part of the bauxite is removed, giving rise to a solution of sodium aluminate, seeded with an aluminium hydroxide crystal and allowed to cool which causes the remaining aluminium hydroxide to precipitate from the solution; some of the aluminium hydroxide is used to seed the next batch, while the remainder is calcined at over 1000 °C in rotary kilns or fluid flash calciners to produce aluminium oxide. The alumina content of the bauxite used is about 50%, but ores with a wide range of alumina contents can be used; the aluminium compound may be present as boehmite or diaspore. The tailings/residue invariably has a high concentration of iron oxide which gives the product a characteristic red colour.
A small residual amount of the sodium hydroxide used in the process remains with the tailings, causing the material to have a high pH/alkalinity >12. Various stages in the solid/liquid separation process are introduced to recycle as much sodium hydroxide as possible from the residue back into the Bayer Process in order to make the process as efficient as possible and reduce production costs; this lowers the final alkalinity of the tailings making it easier and safer to handle and store. Red mud is composed of a mixture of metallic oxides; the red colour arises from iron oxides. The mud is basic with a pH ranging from 10 to 13. In addition to iron, the other dominant components include silica, unleached residual alumina, titanium oxide; the main constituents of the residue after the extraction of the aluminium component are insoluble metallic oxides. The percentage of these oxides produced by a particular alumina refinery will depend on the quality and nature of the bauxite ore and the extraction conditions.
The table below shows the composition ranges for common chemical constituents, but the values vary widely: Mineralogically expressed the components present are: In general, the composition of the residue reflects that of the non-aluminium components, with the exception of part of the silicon component: crystalline silica will not react but some of the silica present termed, reactive silica, will react under the extraction conditions and form sodium aluminium silicate. Discharge of red mud is hazardous environmentally because of its alkalinity. In 1972 there was a Red Mud discharge off the coast of Corsica by the Italian company Montedison; the case is important in international law governing the Mediterranean sea. In October 2010 one million cubic meters of red mud from an alumina plant near Kolontár in Hungary was accidentally released into the surrounding countryside in the Ajka alumina plant accident, killing ten people and contaminating a large area. All life in the Marcal river was said to have been "extinguished" by the red mud, within days the mud had reached the Danube.
However, the long-term environmental effects of the spill have been minor. Tailings storage methods have changed since the original plants were built; the practice in early years was to pump the tailings slurry, at a concentration of about 20% solids, into lagoons or ponds sometimes created in former bauxite mines or depleted quarries. In other cases, impoundments were constructed with dams or levees, while for some operations valleys were dammed and the tailings deposited in these holding areas, it was common practice for the tailings to be discharged into rivers, estuaries, or the sea via pipelines or barges. All disposal in the sea and rivers has now stopped; as residue storage space ran out and concern increased over wet storage, since the mid-1980s dry stacking has been adopted. In this method, tailings are thickened to a high density slurry, deposited in a way that it consolidates and dries. An popular storage method is filtration whereby a filter cake (typically <30%
The mineral pyrite, or iron pyrite known as fool's gold, is an iron sulfide with the chemical formula FeS2. Pyrite is considered the most common of the sulfide minerals. Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold; the color has led to the nicknames brass and Brazil used to refer to pyrite found in coal. The name pyrite is derived from the Greek πυρίτης, "of fire" or "in fire", in turn from πύρ, "fire". In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel. By Georgius Agricola's time, c. 1550, the term had become a generic term for all of the sulfide minerals. Pyrite is found associated with other sulfides or oxides in quartz veins, sedimentary rock, metamorphic rock, as well as in coal beds and as a replacement mineral in fossils, but has been identified in the sclerites of scaly-foot gastropods. Despite being nicknamed fool's gold, pyrite is sometimes found in association with small quantities of gold.
Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin–type gold deposits, arsenian pyrite contains up to 0.37% gold by weight. Pyrite enjoyed brief popularity in the 16th and 17th centuries as a source of ignition in early firearms, most notably the wheellock, where a sample of pyrite was placed against a circular file to strike the sparks needed to fire the gun. Pyrite has been used since classical times to manufacture copperas. Iron pyrite was allowed to weather; the acidic runoff from the heap was boiled with iron to produce iron sulfate. In the 15th century, new methods of such leaching began to replace the burning of sulfur as a source of sulfuric acid. By the 19th century, it had become the dominant method. Pyrite remains in commercial use for the production of sulfur dioxide, for use in such applications as the paper industry, in the manufacture of sulfuric acid. Thermal decomposition of pyrite into FeS and elemental sulfur starts at 540 °C. A newer commercial use for pyrite is as the cathode material in Energizer brand non-rechargeable lithium batteries.
Pyrite is a semiconductor material with a band gap of 0.95 eV. Pure pyrite is n-type, in both crystal and thin-film forms due to sulfur vacancies in the pyrite crystal structure acting as n-dopants. During the early years of the 20th century, pyrite was used as a mineral detector in radio receivers, is still used by crystal radio hobbyists; until the vacuum tube matured, the crystal detector was the most sensitive and dependable detector available – with considerable variation between mineral types and individual samples within a particular type of mineral. Pyrite detectors occupied a midway point between galena detectors and the more mechanically complicated perikon mineral pairs. Pyrite detectors can be as sensitive as a modern 1N34A germanium diode detector. Pyrite has been proposed as an abundant, non-toxic, inexpensive material in low-cost photovoltaic solar panels. Synthetic iron sulfide was used with copper sulfide to create the photovoltaic material.. More recent efforts are working toward thin-film solar cells made of pyrite.
Pyrite is used to make marcasite jewelry. Marcasite jewelry, made from small faceted pieces of pyrite set in silver, was known since ancient times and was popular in the Victorian era. At the time when the term became common in jewelry making, "marcasite" referred to all iron sulfides including pyrite, not to the orthorhombic FeS2 mineral marcasite, lighter in color and chemically unstable, thus not suitable for jewelry making. Marcasite jewelry does not contain the mineral marcasite. China represents the main importing country with an import of around 376,000 tonnes, which resulted at 45% of total global imports. China is the fastest growing in terms of the unroasted iron pyrites imports, with a CAGR of +27.8% from 2007 to 2016. In value terms, China constitutes the largest market for imported unroasted iron pyrites worldwide, making up 65% of global imports. From the perspective of classical inorganic chemistry, which assigns formal oxidation states to each atom, pyrite is best described as Fe2+S22−.
This formalism recognizes. These persulfide units can be viewed as derived from hydrogen disulfide, H2S2, thus pyrite would be more descriptively, not iron disulfide. In contrast, molybdenite, MoS2, features isolated sulfide centers and the oxidation state of molybdenum is Mo4+; the mineral arsenopyrite has the formula FeAsS. Whereas pyrite has S2 subunits, arsenopyrite has units, formally derived from deprotonation of H2AsSH. Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe3+3−. Iron-pyrite FeS2 represents the prototype compound of the crystallographic pyrite structure; the structure is simple cubic and was among the first crystal structures solved by X-ray diffraction. It belongs to the crystallographic space group Pa3 and is denoted by the Strukturbericht notation C2. Under thermodynamic standard conditions the lattice constant a of stoichiometric iron pyrite FeS2 amounts to 541.87 pm. The unit cell is composed of a Fe face-centered cubic sublattice into.
The pyrite structure is used by other compounds MX2 of trans
Porgera Gold Mine
The Porgera Gold Mine is a large gold and silver mining operation in Enga province, Papua New Guinea, located at the head of the Porgera Valley. The mine is situated in the rain forest covered highlands at an altitude of 2,200 to 2,700 m, in a region of high rainfall and frequent earthquakes; the Porgera Gold Mine is operated by the Porgera Joint Venture. It began production in 1990 and was developed and operated by Placer Dome, acquired in 2006 by Barrick Gold, the world's largest gold mining company at that time. Emperor Gold Mine, holding a minority stake of 20%, sold to Barrick in April 2007; this gave Barrick a 95% ownership of the operation. The remaining 5% is owned by Mineral Resources Enga, owned by the Enga Provincial Government, the Papua New Guinea National Government and the Porgera Landowners Association. Barrick Gold Corporation and Zijin Mining Group each own 50% of Barrick Ltd. Porgera Gold Mine is the second largest mine in Papua New Guinea and is regarded as one of the world's top ten producing gold mines.
In 2009 it produced 572,595 ounces of gold and 94,764 ounces of silver and had 2,500 employees and 500 contractors. Since it began operating, the mine has produced more than 16 million ounces of gold and 3 million ounces of silver, accounting for about 12 percent of Papua New Guinea’s total exports; the mine ′ s probable mineral reserves as of 2009 amount to 8.1 million ounces of gold. Porgera Gold Mine is controversial, it has been criticised for environmental and human rights issues. Its own internal investigations have revealed that killings, brutal gang rapes and beatings have carried out by mine security personnel. Porgera Gold Mine began operation in 1990. An underground operation, open-pit mining became important after 1993, temporarily putting an end to underground mining in 1997. Since 2002 the mine utilises both underground mining methods for ore extraction; the site of the current open pit is Mt Waruwari, being excavated. The open pit mine moves about 160,000 tonnes of rock material and gold-bearing ore per day, the underground mine over 2,000 tonnes.
Ore is processed in a conventional plant, utilising several SAG and Ball mills, four Autoclaves, floatation cells and CIP / CIL. Gravity recovery is used, Knelson concentrators doing the primary recovery, with an Acacia Reactor treating the concentrate. A large fleet of Cat 777 and Cat 789 trucks haul on the surface, fed by O&K shovels, smaller excavators and loaders. A collection of underground development and production drilling equipment break ground, bogged by Elphinstone RH series LHD's into a fleet of Elphinstone AD45 trucks; the mine is owned by a Canadian mining company. The mine is nominally a joint venture, however it is managed by Barrick Gold personnel, who are employed on a fly in fly out basis; as of July 2007, all departmental managers are of white extraction. None of the management team lives in the Porgera region, all are accommodated in the mines camp facilities; the mine has an extensive training and education program, offers diverse traineeships and apprenticeships to local people.
This has resulted in many people gaining the necessary skills for employment at the Porgera mine and at other mining operations in Papua New Guinea and other countries. In 2009, out of a total of 2,427 employees at the mine, 93.49% were PNG nationals, 1,606 were Porgerans, 33 other Engans, 630 other PNG nationals, 158 were expatriates. The mine was one of the world’s major low-cost gold producers, but operating costs have increased. In 2004 it produced over one million ounces of gold at a cash cost of US$192 per ounce, its output fell to about 865,000 ounces in 2005, has reached 572,595 ounces of gold at cash costs of US$515 per ounce in 2009. With its 2,500 employees and 500 contractors it is one of the largest gold mines in Papua New Guinea and Australasia, is regarded as one of the world's top ten producing gold mines; the mine has had a large impact on its immediate local area. While modern health care and education services have been brought to the valley by the mine, some members of the community have profited from the mine's presence.
On 23 April 2007 local landowner groups protesting over proposed relocation settlements were successful in peacefully halting mining and processing operations at the mine. The suspension lasted for 10 days, during which various local landowner clans, PNG government representatives and PJV mine management reached a form of agreement on how best to move on; the mine employs its own security force, numbering somewhere between 500 persons. Some sections of the security force are licensed to utilise lethal force. Police and security guards have killed 8 people to 14 people over the past ten years, injured many more. In 2009 rising insecurity around the mine led the government of Papua New Guinea to deploy several squads of mobile policemen to Porgera. According to Amnesty International, the deployment resulted in the eviction of nearby villagers and the burning of their houses. Human Rights Watch investigated and documented reports of abuse, including brutal gang rapes and beatings, carried out by security personnel at the mine.
Barrick Gold, after having denied previous claims of crimes committed at the mine, launched an internal investigation which confirmed the findings. The mine practises riverine tailings disposal, by which processed ore is dumped directly into the local river; this results in an increased sediment loading of 8 million tonnes per year. Additionally, the min