Gold mining

Gold has been prized by humans since prehistoric times. Archaeological evidence suggests that humans were mining gold as far back as 4000 BCE, with some the earliest known gold artifacts dating back to ancient Mesopotamia.[4] Particularly in the region of present-day Iraq, gold was mined extensively. The ancient Sumerians, around 2500 BCE, developed sophisticated tehcniques for extracting gold from alluvial deposiits and underground mines.[5] These techniques included the use of sluice boxes.

Evidence suggests that Nubia had sporadic access to gold nuggets during the Neolithic and Prehistoric Period.[6] Gold mining in Egypt involved both surface mining such as panning for gold in riverbeads and underground mining, where tunnels were dug to extrac gold-bearing quartz veins.[6] During the Bronze Age, sites in the Eastern Desert became a great source of gold-mining for nomadic Nubians, who used "two-hand-mallets" and "grinding ore extraction." By the Old Kingdom, the oval mallet was introduced for mining. By the Middle Kingdom, stone mortars to process ores and a new gold-washing technique were introduced. During the New Kingdom, Nubian mining expanded under Egyptian occupation with the invention of the grinding mill.[6][7] Additionally, gold was associated with the sun god Ra and was believed to be eternal and indestructible, symbolising the pharoah's divine power and afterlife.[8] Gold has also been found in the tombs of Tutankhamun and other pharoahs.[9]

During the Bronze Age, gold objects were also plentiful; especially in Ireland and Spain.[10] Romans employed slave labour and used hydraulic mining methods, such as hushing and ground sluicing on a large scale to extract gold from extensive alluvial (loose sediment) deposits, such as those at Las Medulas.[11][12] Mining was under the control of the state but the mines may have been leased to civilian contractors some time later. The gold served as the primary medium of exchange within the empire, and was an important motive in the Roman conquest of Britain by Claudius in the first century AD; although there is only one known Roman gold mine at Dolaucothi in west Wales. Gold was a prime motivation for the campaign in Dacia when the Romans invaded Transylvania in what is now modern Romania in the second century AD. The legions were led by the emperor Trajan, and their exploits are shown on Trajan's Column in Rome and the several reproductions of the column elsewhere (such as the Victoria and Albert Museum in London).[13] Under the Eastern Roman Empire Emperor Justinian's rule, gold was mined in the Balkans, Anatolia, Armenia, Egypt, and Nubia.

In the area of the Kolar Gold Fields in Bangarpet Taluk, Kolar district of Karnataka state, India; gold was first mined prior to the 2nd and 3rd century AD by digging small pits. Golden objects found in Harappa and Mohenjo-daro have been traced to Kolar through the analysis of impurities – the impurities include 11% silver concentration, found only in KGF ore.The Champion reef at the Kolar gold fields was mined to a depth of 50 metres (160 ft) during the Gupta period in the fifth century AD. During the Chola period in the 9th and 10th century AD, the scale of the operation grew. The metal continued to be mined by the eleventh century kings of South India, the Vijayanagara Empire from 1336 to 1560, and later by Tipu Sultan, the king of Mysore state and the British. It is estimated that the total gold production in Karnataka to date is 1000 tons.[14]

The mining of the Hungarian deposit (present-day Slovakia) primarily around Kremnica was the largest of the Medieval period in Europe.[15]

In South America, gold mining in the Andes dates back to thousands of years, with the Inca empire employing extensive gold mining operations in regsions such as present-day Peru and Ecuador.[16][17] They used stone tools and simple mining techniques to extract gold from rivers, streams, and surface deposits.[16][17]

During the Middle Ages, Europe experience several gold rushes. Most notably in regions like Transylvania, Scotland, and Wales. These rushes were often small-scale and localised compared to later rushes in history.

The Transylvania gold rush took place in present-day Romania, primarily in the region of Transylvania during the medieval period. Transylvania was known for its rich mineral resources including gold, silver, and other metals.[18][19] Miners in Transylvania used both surface and underground mining techniques to extract gold from alluvial deposits and veins. These methods include panning, sluicing, and rudiementary shaft mining.[20]

The Scottish gold rush occurred in Scotland, primarily in the Highlands during the 16th and 17th century. Gold deposits were discovered in rivers and streams, leading to a surge in prospecting and mining activity.[21][22] The Scottish Crown took an interest in gold discoveries, in hopes of aiding the kingdom's economy and revenue. King James IV of Scotland estbalished a royal mint to produce gold coins from Scottish gold. The Scottish gold rush eventually waned due to a combination of factors including the depletion of easily accessible gold deposits, harsh weather conditions, and the political instability at the time.[21]

The Welsh gold rush occurred in Wales, more so in the Dolgellau area of Gwynedd, during the 19th century.[23] Gold deposits were discovered in Welsh mountains, with reports of gold being found in rivers Mawddach and Tryweryn. By the mid-19th century, commercial mining operations had begun. Wales' gold gained popularity for its quality and rarity, leading to its use in royal jewelry for the British royal family.[23][24]

During the 19th century, numerous gold rushes in remote regions around the globe caused large migrations of miners, such as the California Gold Rush of 1849. This is one of the most famous gold rushes in history. The discovery of gold at Sutter's Mill in California sparked a massive migration of people from around the world to California in search of gold. The rush significantly accelerated westward expansion in the United States and had profound effects on the region's economy and society.

The gold rushes began in 1851 when Edward Hargraves, a prospector, discovered gold near Bathhurst, New South Wales.[25] The most well known gold rush in Australia was the Victorian Gold Rush. Thousands of people, known as 'diggers', came from around the world to Australia in search of gold, which ultimately contributed to the growth of cities like Melbourne and Sydney.[26]

The discovery of gold in the Witwatersrand led to the Second Boer War and ultimately the founding of South Africa.[27] This transformed the region into one of the wealthiest gold-producing areas in the world. This rush played a crucial role in the developmenet of South Africa's economy and lead to the estbalishment of Johannesburg, known as the 'city of gold'.[27][28] Gold-bearing reefs in the neighbouring Free State province were found shortly thereafter, driving significant development in the region with the establishment of the Free State goldfields.[27][28][29]

Also known as the Yukon Gold Rush, brought prospectors from around the world to the Klondike region of the Yukon territory in Canada.[30][31] The Klondike God Rush began in 1896, when gold was discovered in Bonanza Creek, a tributary of the Klondike River by George Carmack and his Indigenous companions, Skookum Jim Mason and Tagish Charlie.[32] As prospectors arrived in Klondike, makeshift towns and settlements sprang up along the rivers, including Dawson City, which because the largest town in Yukon at the height of the gold rush.[33] Prospectors employed various mining techniques to extract gold from the Klondike's streams and riverbeds, including placer mining, dredging, and hydraulic mining.[34]

The Carlin Trend of Nevada, U.S., was discovered in 1961. Official estimates indicate that total world gold production since the beginning of civilization has been around 6,352,216,000 troy ounces (197,576.0 t) and total gold production in Nevada is 1.1% of that, ranking Nevada as one of the Earth's primary gold-producing regions.[35][36]

Hard rock mining extracts gold encased in rock, rather than fragments in loose sediment, and produces most of the world's gold. Sometimes open-pit mining is used, such as at the Fort Knox Mine in central Alaska. Barrick Gold Corporation has one of the largest open-pit gold mines in North America located on its Goldstrike mine property in north eastern Nevada. Other gold mines use underground mining, where the ore is extracted through tunnels or shafts. South Africa has the world's deepest hard rock gold mine up to 3,900 metres (12,800 ft) underground. At such depths, the heat is unbearable for humans, and air conditioning is required for the safety of the workers. The first such mine to receive air conditioning was Robinson Deep, at that time the deepest mine in the world for any mineral.[40]

Gold is also produced by mining in which it is not the principal product. Large copper mines, such as the Bingham Canyon mine in Utah, often recover considerable amounts of gold and other metals along with copper. Sand and gravel pits, like those in Denver (Colorado), may recover small amounts of gold in their wash operations. The largest producing gold mine in the world, the Grasberg mine in Papua, Indonesia, is primarily a copper mine.[41]

Placer mining is a method of extracting gold from alluvial deposits such as sand, gravel, and sediment.[43][44] These are known as placer deposits which are typically found in riverbeds, stream beds, and floodplains.[45] These deposits typically contain minerals that are resistant to weathering and eroision like gold, platinum, diamonds, and more. They are characterized by their relatively high concentration of valuable minerals compared to the surrounding rock or sediments.[43][45] Unlike hard-rock mining, which involves excavating solid rock formations, water or dredging is used to extract the gold.[43]

Using a sluice box to extract gold from placer deposits has long been a very common practice in prospecting and small-scale mining. Sluices work on the principle that heavier particles will sink to the bottom of a stream, while those that are lighter will be carried downstream and expelled.[46][47] A sluice box is essentially a man made channel with riffles set in the bottom. The riffles are designed to create dead zones in the current to allow gold to drop out of suspension.[46][47] The box is placed in the stream to channel water flow. Gold-bearing material is placed at the top of the box. The material is carried by the current through the volt where gold and other dense material settles out behind the riffles. Less dense material flows out of the box as tailings.[46][47]

Larger commercial placer mining operations employ screening plants, or trommels, to remove the larger alluvial materials such as boulders and gravel, before concentrating the remainder in a sluice box or jig plant.[48] After the gold is sorted through trommels, it is then placed through regular sluice boxes for further sorting.[48] These operations typically include diesel powered, earth moving equipment including excavators, bulldozers, wheel loaders, and rock trucks.

Although this method has largely been replaced by modern methods, some dredging is done by small-scale miners using suction dredges. These are small machines that float on the water and are usually operated by one or two people. A suction dredge consists of a sluice box supported by pontoons, attached to a suction hose which is controlled by a miner working beneath the water. This method is particularly popular in areas where gold is found at river bottoms or submerge deposits.[49][50]

Suction dredging can have environmental impacts, moreso on aquatic habitats and water quality.[51] Regulations and best practices are often in place to minimize these impacts.[51] State dredging permits in many of the United States gold dredging areas specify a seasonal time period and area closures to avoid conflicts between dredgers and the spawning time of fish populations. Some US states, such as Montana, require an extensive permitting procedure, including permits.

Some large suction dredges [100 horsepower (75 kW) & 250 mm (10 in)] are used in commercial production throughout the world. Small suction dredges are much more efficient at extracting smaller gold than the old bucket line. This has improved the chances of finding gold. Smaller dredges with 50-to-100-millimetre (2 to 4 in) suction tubes are used to sample areas behind boulders and along potential pay streaks, until "colour" (gold) appears.

Other larger scale dredging operations take place on exposed river gravel bars at seasonal low water. These operations typically use a land based excavator to feed a gravel screening plant and sluice box floating in a temporary pond. The pond is excavated in the gravel bar and filled from the natural water table.[46] "Pay" gravel is excavated from the front face of the pond and processed through the floating plant, with the gold trapped in the onboard sluice box and tailings stacked behind the plant, steadily filling in the back of the pond as the operation moves forward.[46] This type of gold mining is characterized by its low cost, as each rock is moved only once. It also has low environmental impact, as no stripping of vegetation or overburden is necessary, and all process water is fully recycled. Such operations are typical on New Zealand's South Island and in the Klondike region of Canada.[52]

Also called a cradle, a rocker box uses riffles located in a high-walled box to trap gold in a similar manner to the sluice box. A rocker box uses less water than a sluice box and is well suited for areas where water is limited. A rocking motion provides the water movement needed for the gravity separation of gold in placer material.[46] Rocker boxes gained popularity during the California Gold Rush in the 19th century and remain in use today.[46][53] Although simple and inexpensive, it is not efficient as the previously discussed mining techniques.[54][55]

The dominant method for refining gold is a cyanide extraction method, or gold cyanidation, introduced in the late 1800s. This a metallurgical technique used to extract gold from lower grade ores by converting gold into a water-soluble coordination complex.[56][57] Finely ground rock is treated with a solution of sodium cyanide. The extract is absorbed onto carbon and then removed from the carbon with a solution of caustic soda and cyanide. Gold cyanide is then converted to relatively pure gold through gold parting.[56][57]

There are many environmental hazards associated with this extraction method, largely due to the high toxicity of the cyanide compounds. Furthermore, there are potentials for accidental spills or leaks to cause harm to aquatic ecosystems and human health.[58][59] For example, in 2000, the Baia Mare cyanide spill in northern Romania released approximately 100,000 cubic metres (3,500,000 cu ft) of waste water contaminated with heavy metal sludge and up to 120 long tons (122 t) of cyanide into the Tisza River.[60]

Historically, mercury was used extensively in placer gold mining in order to form mercury-gold amalgam with smaller gold particles, and thereby increase the gold recovery rates.[61] First, the gold ore is crushed and ground to a fine powder to expose the gold particles for amalgamation. Then, this finely ground ore is mixed with liquid mercury to amalgamate it.[62] Mercury forms an amalgam, an alloy, with gold particles to allow for the efficient capture of gold from the ore. The gold is concentrated by boiling away the mercury from the amalgam. This process is called retorting.[63] This is effective in extracting very small gold particles, but the process is hazardous due to the toxicity of mercury vapour.[61][64] Large-scale use of mercury stopped in the 1960s. However, mercury is still used in artisanal and small-scale gold mining (ASGM).[61][65]

While most gold is produced by major corporations, there are an estimated 10 to 15 million small-scale artisanal gold miners worldwide. Around 4.5 million of them are women, and an estimated 600,000 children work in illegal artisanal gold mines. Artisanal miners use rudimentary methods to extract and process gold. Many of these people are mining to escape extreme poverty, unemployment and landlessness.

In Ghana, galamsey miners are estimated to number 20,000 to 50,000.[66] In neighboring francophone countries, such workers are called orpailleurs. In Brazil, Venezuela, Suriname, and French Guiana, workers are called garimpeiros.[67][68][69] These workers are not required to claim responsibility for their social and environmental impacts.[70][71]

Miners risk government persecution, mine shaft collapses, and toxic poisoning from unsafe chemicals used in processing, such as mercury. For example, in Ghana during 2009, the Dompoase mine collapse killed 18 workers. It was the worst mining disaster in Ghanaian history.[66]

Children in these mines suffer extremely harsh working conditions and various hazards such as collapsing tunnels, explosions, and chemical exposure. Children may be especially vulnerable to these hazards and many suffer from serious respiratory conditions, hearing, and vision problems.[72]

Gold mining by large multi-national corporations produces about 80% of the gold supply. Most gold is mined in developing nations. Large mining companies play a key role in globalisation of the economy by linking rich and poor companies.[73] Newmont and Barrick Gold are the largest gold mining companies in the world, but there are many smaller corporations in the industry.[74]

Local communities are frequently vulnerable to environmental degradation caused by large mining companies and may lack government protection or industry regulation.[73] For example, thousands of people around Lega Dembi mine are exposed to mercury, arsenic, and other toxins resulting in widespread health problems and birth defects.[75] Vulnerable communities may also lose their land to the mine.[76] Some large companies have attempted to build local legitimacy through corporate responsibility initiatives and local development.[73][76]

Gold mining can significantly alter the natural environment. Gold mining activities in tropical forests are increasingly causing deforestation along rivers and in remote areas rich in biodiversity.[77][78] Mining has increased rainforest loss up to 70km beyond lease boundaries, causing nearly 11,670 km² of deforestation between 2005 to 2015.[79] Up to 9% of gold mining occurs outside of these regulated lease boundaries.[79] Other gold mining impacts, particularly in aquatic systems with residual cyanide or mercury (used in the recovery of gold from ore), can be highly toxic to people and wildlife even at relatively low concentrations.[80] Illegal gold mining exacerbates the ecological vulnerability of the remaining forest ultimately leading to permanent forest loss.[81] Gold mining clears native forests for mineral extraction, but also indirectly facilitates access to more land and further clearing. Rainforest recovery rates are the lowest ever recorded for tropical forests, with there being little to no tree regeneration at abandoned mining camps, even after several years.[82] The Amazon rainforest is at risk for 'savannization', which is the gradual transformation of a tropical rainforest into a savannah.[83][84] This would ultimately lead to a collapse of biodiversity, ecosystems, and climate.[84][85]

Gold mining produces more waste than mining of other minerals, because it can be mined at a lower grade. Tailings can contain lead, mercury, cadmium, and arsenic. These toxins can pose health risks for local communities.[86] Arsenic is typically found in gold-containing ores, and gold processing may contaminate groundwater or the atmosphere. This pollution may persist for decades.[87] Furthemore, mining operations use large quantities of water for processing ore and can result in the contamination of water sources with heavy metals, such as mercury and cyanide, used in the extraction process.[88][89] This pollution can have detrimental effects on aquatic ecosystems and human heatlh. Soil degradation has also been found to be impacted by gold mining.[90][79][91] Mining activities can disturb soil structure, leading to erosion, sedimentation of waterways, and loss of fertile land for agriculture or vegetation regrowth.[79][91] More evidently, dust and emissions from mining machiner and processing facilities can contribute to air pollution, impacting air quality and potentially causings respiratory problems for nearby communities.[92][93]

Large-scale gold mining projects may require land acquisition and resettlement of local communities, leading to displacement, loss of livelihoods, and disruption of traditional ways of life.[94][95] In addition to the possible respiratory problems that could be acquired, individuals may be exposed to hazardous chemicals used in gold extraction such as mercury and cyanide. These chemicals pose risks to gold miners, communities, and wildlife; resulting in further medical problems involving neurological disorders and waterborne diseases.[96][97]

Gold mining in some regions has been associated with conflicts over land rights, labour rights violations, and exploitation of vulnerable populations, including Indigenous peoples and artisanal miners.[98][99] Mining activities can damage or destroy cultural heritage sites, artifacts, and sacred areas; further impacting cultural identities and heritages. In the Amazon rainforest, Indigenous peoples have been killed and had their rightfully owned land stolen from them.[100] As a consequence of this, some have left the rainforest to move to cities which further puts them at risk to disease, homelessness, and poverty.[100][101]

Artisanal gold mining is widespread across Africa, occurring in numerous countries including Ghana, Mali, Burkina Faso, Tanzania, Zimbabwe, and many others.[102] For many individuals and communities in rural Africa, artisanal gold mining represents a critical source of income and livelihood, providing employment opportunities and economic support in regions with limited alternative options.[103][104] Artisanal mining operations vary in scale, from individuals panning for gold in rivers and streams, to small groups working collectibely in informal mining camps, often referred to as 'galamsey' in West Africa.[105]

Gold mining can create employment opportunities in mining operations and related sectors. Howevers, these jobs may be temporary. The sector's reliance on fluctuating global gold prices can lead to economic stability for communities dependent on mining. The discovery of significant gold deposits in a region often sees a flood of resources and development, which lasts as long as the mines are economic. When goldfields begin to decline in production, local economies find themselves destabilised and overly reliant upon an industry that will inevitably abandon the region when gold deposits are sufficiently depleted; [106][107] leaving the areas without proper rehabilitation.[107]

The some instances, the 'resource curse' phenomenon may occur, where countries rich in natural resources, like gold, may experience economic challenges, corruption, inequality, and governence issues instead of sustained development.[108] Despite the existence of several laws that regulate environmental crimes, illegal practices in mining tends to happen because of an absence of enforcement.[109] The rules for gold mining create ambiguities between the types of 'legal' mining; leaving loopholes for those to exploit.[109]

Gold prices are subject to global market trands, economic uncertainties, and geopolitical factors. Fluctuation in gold prices can influence invesment decisions, currency values, and trade balances in gold-producing and consuming countries.[110][111] Furthermore, the global gold supply chain involves complex networks of mining companies, refineries, traders, and retailers. Ensuring ethical and sustainable practices throughout this supply chain, including addressing issues such as child labour and environmental degradation, remains a challenge.

Human Rights Watch produced a report in 2015 that outlined some of challenges faced globally. The report notes that

Thousands of children in the Philippines risk their lives every day mining gold. Children work in unstable 25-meter-deep pits that could collapse at any moment. They mine gold underwater, along the shore, or in rivers, with oxygen tubes in their mouths. They also process gold with mercury, a toxic metal, risking irreversible health damage from mercury poisoning.[112]

Fairtrade and Fairmined dual certification for gold was launched across the United Kingdom on 14 February 2011,[113] a joint scheme between The Fairtrade Foundation and The Association for Responsible Mining. The Fairmined mark ensures that the gold has been extracted in a fair and responsible manner.

A UN investigation reported human rights abuses such as sexual exploitation of women and children, mercury poisoning, and child labor affecting communities where illegal gold production occurs. The reports said global buyers such as Switzerland, through which roughly two-thirds of global trade transits, need to ensure that human rights are respected throughout supply chains.[114]

The "No Dirty Gold" campaign, working with a number of campaigning partners, was established in 2004 and aims "to ensure that gold mining operations respect human rights and the environment" through a call for changes in gold mining techniques and processes.[115][116] The impacts of mining on the environment are long-lasting, and active land management and restoration are needed to ensure recovery.[117] A barrier to the restoration of environments is cost. Limited funding is a major barrier in implementing commitments.[118] Restoration costs vary widely between difference approaches, such as passive and active restoration.[119][120] Additionally, governments have started to promote the formalization of gold mining.[121] This formalization puts the government in a better position to govern the sectors, manage environmental impacts, and direct mining away from ecologically sensitive areas.[121][122]

World gold demand (defined in terms of total consumption excluding central banks) in 2007 was 3,519 tonnes.[123] Gold demand is subdivided into central bank reserve increases, jewellery production, industrial consumption (including dental), and investment (bars, coins, exchange-traded funds, etc.)

The supply of gold is provided by mining, official sales (typically gold by central banks), de-hedging (physical delivery of metal sold months before by mining companies on terminal markets), and old gold scraps. The total world supply of gold in 2007 was 3,497 tonnes.[124] Gold production does not need to make up for gold demand because gold is a reusable resource. Currently, yearly gold mining produces 2% of the existing above-ground gold which is 158,000 tonnes (as of 2006).[125] In 2008, gold mining produced 2,400 tonnes of gold, official gold sales close to 300 tonnes, and dehedging (physical delivery of metal sold months before by mining companies on terminal markets) close to 500 tonnes.[126]

World mined gold production has peaked four times since 1900: in 1912, 1940, 1971, and 2001, which each peak being higher than previous peaks. The latest peak was in 2001, when production reached 2,600 metric tons, then declined for several years.[127] Production started to increase again in 2009, spurred by high gold prices, and achieved record new highs each year from 2011 through 2015, when production reached 3,100 tonnes. Early estimates of 2016 gold production indicate that it was flat to 2015 production, at 3,100 tonnes.[128]

In 2009, Barrick CEO Aaron Regent claimed that global production had peaked in 2000.[129] Barrick's production costs have been "trending down" despite this peak, reaching $465 per troy ounce ($15.0/g). In 2006, with gold at $650 per troy ounce ($21/g), Roland Watson claimed that gold production had peaked in 2001 due to falling exploration in the 1990s, when gold prices were low. He predicted that higher prices and new technologies would boost gold production to higher levels in the future.[130]

In July 2012, Natural Resource Holdings CEO Roy Sebag wrote a report entitled "2012 World Gold Deposit Ranking"[131] claiming that gold production would peak between 2022 and 2025 due to the markedly lower grades and remote locations of the remaining known undeveloped deposits.

"Consequently, the guaranteed depletion in the existing production mix coupled with a more realistic introduction of new mines into the mix (as opposed to our theoretical tomorrow scenario) makes it clear that barring multiple high-grade, multi-million ounce discoveries each year, a significant increase in gold production is unlikely. Moreover our calculations point towards gold production peaking at some point between 2022 and 2025 assuming the 90 million troy ounces [2,800 tonnes] per year figure is maintained."

Charles Jeannes, the CEO of Goldcorp, the world's largest gold miner by market capitalization, stated in September 2014 that Peak Gold would be reached in either 2014 or 2015.[132] "Whether it is this year or next year, I don't think we will ever see the gold production reach these levels again," he claimed. "There are just not that many new mines being found and developed."

Central banks diversify their reserves with gold to protect the value of the dollar during challenging economic times.[134] When banks are forced to print more money to prevent economic turmoil they are simultaneously devaluing the currency. Gold, unlike money, is a finite valuable material which can be used as a hedge against the inflation cause by increasing the money supply.[134] Gold has this inverse relationship with the US dollar which is used as a reserve asset by many central banks thus protecting the central banks reserves when there is a dip in the US dollar or the money supply increases.[134]

As mentioned above the value of the U.S. dollar is normally inversely related to the value of gold, this is because gold is dollar-denominated.[133] When the U.S. dollar is stronger it tends to keep the price of gold lower and controlled and when there is a weaker U.S. dollar the price of gold is likely to increase as well as the demand for it.[135]