gold mining and processing: everything you need to know

gold mining and processing: everything you need to know

These advancements, coupled with the progress made in mining technology, have provided for a great deal of growth in the industry of gold mining. Historical documents reveal that gold was being mined in the area of Bulgaria as far back as 7000 years ago. The once primitive, cumbersome mining methods used during that time has developed into compact, efficient modern-day equipment that makes gold mining a more cost-effective, efficient process.

The process begins when geologists take ore samples to determine the best places for companies to mine. Once mining engineers know where gold is located and what other materials surround it, the mining process can begin. If the gold is located close to the surface, its mined with open-pit mining techniques.

Gold thats located farther below the surface is collected with underground mining methods. Large pieces of ore are made into smaller pieces, and then the sand grain-sized pieces are mixed with a cyanide solution to create a watery, mud-like mixture.

Gold mining takes place in countries such as South Africa, Australia, the United States, Canada, China and Pakistan. One of the largest gold mines known worldwide is the Aurora Gold Mine located in Guyana, Africa. As of the year 2013, the Aurora Gold Mine has an estimated reserve of 6.54 million ounces.

In addition to cyanide processing, gold ore is also processed with gravity separation. Advanced technology has enabled the amount of gold mined and processed to steadily increase over the years. For example, the worldwide production of gold in 2006 was 2360 metric tons. As of 2013, that number had climbed to 2770 metric tons. With continued advancements in mining technology, this growth trend is likely to continue.

Thats interesting that there is still gold to be found in the U.S. I would have thought that it was all long gone. It would be pretty cool to go out and accidentally find a gold mine while you were hiking or something.

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When it comes to buying the right equipment for your mining operation, there are a number of factors to consider. From your budget to the size of your operation and beyond, its important to do the research so you install the equipment that is going to help your operation thrive. But youve likely already considered []

When it comes to buying the right equipment for your mining operation, there are a number of factors to consider. From your budget to the size of your operation and beyond, its important to do the research so you install the equipment that is going to help your operation thrive. But youve likely already considered []

Every day, 6,300 people die as a result of occupational accidents or work-related diseases. Thats more than 2.3 million deaths per year. Since 2003, the International Labour Organization (ILO) has celebrated World Safety Day on April 28. World Safety Day helps raise awareness of occupational safety and health. Through worldwide events and activities on World []

Every day, 6,300 people die as a result of occupational accidents or work-related diseases. Thats more than 2.3 million deaths per year. Since 2003, the International Labour Organization (ILO) has celebrated World Safety Day on April 28. World Safety Day helps raise awareness of occupational safety and health. Through worldwide events and activities on World []

In Denver, Colorado from February 24-27 mining industry professionals from around the world gathered to attend The 2019 SME Annual Conference and Expo. Thousands of key players in the mining and metallurgy market gathered to exchange ideas and discover new technologies to improve their extraction processes. General Kinematics attended this years event, sharing discoveries and []

In Denver, Colorado from February 24-27 mining industry professionals from around the world gathered to attend The 2019 SME Annual Conference and Expo. Thousands of key players in the mining and metallurgy market gathered to exchange ideas and discover new technologies to improve their extraction processes. General Kinematics attended this years event, sharing discoveries and []

gold mining process | introduction |

 integrated report 2013 | anglogold ashanti

gold mining process | introduction | integrated report 2013 | anglogold ashanti

To conduct our business and produce gold, certain inputs such as ore-bearing resources, people and machinery are required. We invest in skills enhancement, technology development and application, and in prospecting for and developing our mineral resources and ore reserves, to ensure the economic viability and sustainability of our business.

Vertical shafts and decline ramps are sunk into the ground to transport people and equipment to and from deep-level ore bodies (many are more than 1,000m below surface) and to bring the ore mined to surface.

Gold ore is processed and smelted into dor (unrefined gold bars) at our operations and dispatched to various metal refineries, including our Queiroz refinery in Brazil and Rand Refinery in South Africa.

Overarching this business model is our sustainability strategy which has as its primary aim zero harm to people and the environment. We endeavour to ensure that the communities with which we engage and society are better off for our presence.

This is integral to mine planning and development, from the start of exploration to the end of mining activity. Closure planning, which takes into account community livelihoods and land rehabilitation, continues throughout the life of an operation.

9 step process for discovering, mining & refining gold

9 step process for discovering, mining & refining gold

In modern times though, mining for gold is a much more intensive, yet sophisticated process. Most surface, or alluvial gold has been found, which is why gold is mainly mined from the earth today. Its largely a matter of technology and requires much expertise and elaborate equipment.

Mining for gold today can essentially be broken down into 9 steps. Continue reading to learn more about how gold is discovered, how its brought out of the ground and how its refined to produce beautiful gold coins, bars, jewelry and other items.

The first step is discovering where gold deposits may be. Geologists use special geology maps to look for promising areas to explore further. They examine physical and chemical characteristics of surface rocks to determine if any gold is in the ground beneath.

Once some promising areas are identified through their geological characteristics, targets for drill testing are outlined using a variety of techniques, including remote sensing, geophysics and geochemistry (both air and ground based).

Next, rock samples are taken through drill testing and analyzed. Geologists and mining engineers use these samples to determine if gold actually exists, the size of the deposit and the quality of gold in the ground beneath. This information is used to determine if enough gold exists under the surface to make mining worthwhile.

If its determined the amount and quality of deposits makes mining worthwhile, engineers will next determine the type of mine thats needed, any physical obstacles and the impact the mine will have on the surrounding environment.

Before any mining can take place, infrastructure like roads and processing facilities must be constructed. Even the simplest open-pit mines can take up to a year to construct before any mining can occur. And since many potential mines are in remote areas, entire infrastructures like roads, administrative offices, equipment storage areas and even whole towns have to be built. Much of the time, it can be up to 5 years between the times discovery is made to when actual mining takes place.

Once ore is extracted, processing it into pure gold must be done. Ore is first crushed and then undergoes various processes depending on the nature of associated minerals. Processing low-grade ore is relatively simple while higher grades require more extensive processing.

Once basic processing is done, the ore is taken to a refinery where the remaining impurities are stripped out. Crude gold is melted and treated with chloride, which converts any remaining foreign metals to chloride which will then drift off the gold. The result is 99.5% pure gold, which is then cast into electrodes (known as anodes) where it is then placed into an electrolytic cell. A current is then passed through the cell, with the end product being 99.99% pure gold.

After a few years, gold reserves in the mine will be exhausted. In the old days, the mine would be boarded up and abandoned. Today though, a reclamation project is done to try and return the land to its previous natural state as much as possible anyway.

As you can see, the process of taking metal ore from the earth and converting it to gold bullion is quite extensive and requires a lot front-end investment and time. In the end though, we get these shiny coins and bars to enjoy.

Gold miners too take special care to make the impact of mining for gold as light as possible. Reclaiming land to its previous natural state is the final and perhaps most important step to ensuring the process of obtaining gold doesnt result in permanent damage to the landscape.

The post on the 9 steps of how gold is refined, has helped me to relate the process of Gods divine will has a child of God, when one is choosen by God, he or she has to go through a process in order to accomplish the will of God and also to embrace others in knowing God. I was inspired spiritually by God in researching the steps and process gold has to go through to become the finest gold.

It seems that many have thought on the gold mentioned in the Bible and having done so, think further about the processing of it spiritually in ones own life. The temple was covered in gold. We go through processes in our lives too so that God can clothe us in His righteousness not our own, and it is a costly process and time-consuming but the value of it will one day be revealed not now but when the process is completed in His time.

tips on reducing the impact of gold mining and processing

tips on reducing the impact of gold mining and processing

Gold has been one of the most valuable commodities since the beginning of time. It has been treasured since the days the Pharoahs of Egypt built their pyramids and the Aztecs paid homage to their god Montezuma. Although gold is a metal full of luster and the universal symbol of wealth, it has a dark side to it. The biggest problem with gold is that its a commodity that leaves a harsh footprint on the environment.

There are a lot of environmental problems associated with gold. It damages the environment when it is mined, smelted and processed. The good news is that these problems can be mitigated with the right steps.

Todays gold rates are on an upward trajectory, with the latest reported prices touching $1,280, testing resistance at $1,300. There are a number of reasons that demand for gold has risen. One is that it is a good hedge against economic instability. Its true that gold has contributed to the global economy, but it has taken a toll on the environment.

The gold rush bolstered the world economy and put wealth into the hands of many opportunistic investors, but rapid industrial gold mining comes at a steep cost to the environment. As it stands, traditional methods of mining gold releases huge swathes of toxic waste and ravages the landscape. In many poorer parts of the world, miners easily get away with using illegal means of obtaining gold.

The worst of such practices is the use of cyanide in mining operations. This toxic chemical is used to process gold because it provides a cheap and effective alternative to remove the lustrous metal from low grade ore. Cyanide has devastating environmental and health effects, affecting not just humans but other animals, with more than 30 major accidents occurring worldwide in the past 25 years.

The gold mining boom has caused destruction on the Amazon rainforest as artisanal and unlicensed gold miners tear down the environment to access hard to reach gold deposits underneath. These illegal gold miners use mercury to extract gold, leaching the toxic chemical into the air and water. About 1,000 tons of mercury is released into the environment every year by the 15 million artisanal gold miners around the world.

Innovative technology only gains mainstream acceptance if it can be implemented economically while not deviating too far from traditional practices. To this end scientists and researchers around the world have found ways to mitigate the environmental impact of the mining industry. Lets go through a few examples:

Zero liquid discharge is when wastewater is processed to be reused for mining activities. The idea is to bring the ratio of disposed wastewater to recovered wastewater down to zero. This allows miners to forego costly disposal processes while making more efficient use of the mining projects water supply. The two most prominent methods that help achieve zero liquid discharge are crystallization and vacuum evaporation.

Many mining operations can be optimized to use less energy for the same output. Some Canadian miners are already striving to make their mining operations less wasteful when it comes to resources. Vehicles are using clean diesel fuels, and in rare cases, green sources of energy. More machines will be powered by alternative sources of energy such as hydrogen fuel cell batteries and solar energy to produce less pollution.

Old mines that have reached maturity are reseeded to cultivate the growth of natural vegetation. The National Mining Association in the US has reported that mining companies have reclaimed around 2.8 million acres of mined land, converting them into wildlife reserves and recreational areas. If nothing else, these older mines are being put to good use and generate income for the local economy.

Gold has not been good for the environment. The good news is that contemporary mining and processing methods can reduce this harmful impact. This is important, since demand for gold is higher than ever.

gold mining and processing | facts and details

gold mining and processing | facts and details

The principle behind panning for gold is that gold is heavier than almost every other substance. By sloshing it around a in slurry of stone, sand and water the heavier gold will settle to the bottom of the pan while the other materials wash away.

All gold found by miners and prospectors originally came from hard rock. The problem with hard rock is that it has to be broken down and often it is located deep in the earth. That is why gold eroded into river bedsso called alluvial, or placer gold---is the easiest to extract. The gold is already broken down and it is easy to get at. The same principal that separates gold from other materials in a pan is what allows gold to concentrate in these alluvial deposits. Geologist also look for gold in ancient river beds. Veins of gold are often found by tracing the alluvial deposits to their source.

Sophisticated operations that use between $1,500 and $5000 worth of equipment use suction dredges that vacuum up gravel, sluices to separate the gravel from the black sand big plastic pans used to actually pan the gold.

Mercury is sometimes used in gold mining. Gold sticks to mercury, and to retrieve the coveted metal the mercury is vaporized, leaving behind the gold. Gold in the Amazon regions of Brazil, Columbia and Venezuela is sometimes mined with huge dredges that scoop up mud and gravel from the bottom of a river. Each ton of muck contains, if the miners are lucky, three-hundredths of an ounce of gold. To extract the gold mercury is added.

There are large deposits of gold and other metals on the ocean floor but are expensive to mine. Some of the richest deposits are me than one kilometer under the sea in massive mineral deposits. Already a project is underway off Papua New Guinea to extract such gold using a 160-ton remote controlled machine developed by oil companies to dig trenches for pipelines. Perhaps the biggest problem is that richest deposits are found around underwater vents that are also rich in unique life forms such as two-meter-long tube worms and blind shrimp.

Edwin Kiester, Jr wrote in Smithsonian magazine, When the cry of "Gold!" went up in California in 1848, the pioneering prospectors had little to do but pluck flakes and nuggets of gold out of streams. Those easy pickings didn't last long. Miners then moved on to panning, in which gravel and water are gently rocked in a handheld pan until the water gradually carries away the gravel and leaves the heavier gold behind. Placer mining, panning on a grand scale, uses sluices and flumes to separate gravel and gold. Hard-rock mining tunnels into the earth to extract gold ore from buried veins. [Source: Edwin Kiester, Jr, Smithsonian magazine, August 1999] Eventually, miners hit upon the cheapest way of "getting gold out of the secret places." Hydraulic mining applied a simple method familiar to all who've used a garden hose. Direct a forceful stream of water at the earth, and it will carve a ditch and carry away the loosened soil. Harnessing water under powerful pressure thus could blast away the hillsides concealing gold ore. Then the water and earth could be fed through sluices and riffles to catch the gold. In the late 1860s, Julious Poquillon bought up cheap land along the Yuba River...and the North Bloomfield Gravel Mining Company was launched. [Ibid]

Hydraulic mining was born and raised here in California," California park ranger Ken Huie told Smithsonian magazin. "And no matter what you think of the result, it was a tremendous engineering feat." The key to success was lots and lots of water, year-round, in dry seasons as well as wet. Engineers built a network of reservoirs, lakes, ditches and flumes extending as far as 40 miles to catch every precious drop of rain or Sierra snowmelt. Propelled by gravity along a vertical drop of up to 500 feet, the captured waters converged into a single, powerful stream. Then they were fed into water cannons trained on the gold-bearing hillside. [Ibid]

A single monitor [water cannon] with an eight-inch nozzle like this could direct 16,000 gallons of water a minute," he says. "It could tear away 4,000 cubic yards of earth from the hillside every day." Into the sluices went the result, out came the gold, and the rest was dumped into the Yuba and sent downstream. And what a load the river carried! Tons and tons of earth, rocks, trees, shrubbery, silt and a mucky mixture of mud, sand and gravel known as "slickens." The once-crystal Yuba turned chocolate brown. So did the Feather River, into which the Yuba emptied, and the Sacramento. The brown waters extended all the way to San Francisco Bay. [Ibid]

It's an irony, isn't it?" said after showing a mile-and-a-half-long tunnel that drained the mine. "It cost the company about three and a half million dollars to construct all this. And all they got back, according to the best estimates, is three and a half million. For all the effort and the damage, they just about broke even. [Ibid]

In 1887, John Stewert McArthur patented the McArthur-Forest process for using cyanide to extract gold from ore, making it easier to extract gold from lower quality such as what is found in relative abundance in South Africa. [Ibid]

Describing the gold mining process in Victoria Australia, NicK Fields wrote in Times of London: Machines pound the the gold-flecked earth into a toothpaste-like consistency before using bacteria to liberate the precious metal. It is a laborious process for the mines 350 workers, who toll around the clock in the uncomfortably high temperature so deep underground. The miners make up to $100,000 a year.

It is extraordinarily hot and the stench of ammonia is unbelievable. Yet here, 600 meters below the ground, 350 workers are at work recovering gold from the Victorian bushlands....A fleet of jumbo machines dig trenches at 20 meter intervals off the central pathway. They are used to slice the earth into 15-meter-high stopes, a Cornish word for the large chambers created by the miners before the earth is taken from the surface. [Ibid]

Each 40 tone dirt-filled lorry leaving the mine yields only two teaspooons of gold, when processed, The rubble is pounded and bars of buillion are produced on site before being shipped to Perth once a week. [Ibid]

The world's largest known gold deposit and world' third largest copper reserves are located on 13,000 foot-high mountain, the Grasberg Mountain in south central Irian Jaya not far from 16,024-foot Puncak Jaya, highest mountain in Indonesia and Southeast Asia and the only one between the Andes and the Himalayas that has a glaciers. There are also large deposits of silver. [Source: Mark Frankel, Newsweek, December 18, 1995]

The mountain is being mined by the New Orleans-based Freeport McMoRan Copper and Gold Company through its Indonesian subsidiary PT Freeport Indonesia. The company has spent $3 billion to develop the mine and extract its minerals and is the largest single American investor in Indonesia, with a market capitalization of $5 billion, and the country's most profitable business, making more than $1 million a day.

Freeport has access to nine million acres of land, an area one and half times the size of Vermont. About 1.24 million acres is taken up by the mine. The operation is also one of the worlds largest copper mines. The 60,000 people employed at the mine live on a compound carved out of the jungle with American-style shopping centers.

The mine straddles a mineral-rich ridge of mountains pushed up by a collision between the Pacific and Australian tectonic plates. Everyday about $7.2 million worth of gold, copper and silver is extracted from the Grasber mine. The refined metal harvested every year is worth about $2 billion. The total deposit, one of the world's richest, is worth at least $50 billion.

The Freeport McMoRan Gold Mine is the worlds largest gold and copper mine. It is is an open-pit mine on the top of a mountain. It will be more than two miles across at the end of its working life, sometime around 2015. To get to it you need to pass through two tunnels and then climb an incredibly steep road that is so dangerous drivers need a special permit to traverse it.

The ore is dug us with huge shovels and loaded onto trucks that coast $2 million a piece and moved to a processing plant that crushes and chemically concentrates the ore into a slurry that is piped 75 miles to the coast, where it is shipped to smelters. The work continues 24 hours a day, seven days a week. More than 200 tons of ore is pried loose form the rock every day.

Describing the mining process, Thomas O'Neil wrote in National Geographic, "Shivering in the cold wind...I watched trucks with tires ten feet high haul out ore that would be processed into a gray concentrate of copper, gold and silver. The mix, piped in a slurry from down the mountain to the private seaport of Amamapare, is dried and shipped to smelters round the world. Everything is jumbo size: the workforce of 17,000; the gold, an estimated 40 million ounces, the single biggest gold reserve in the world; the copper deposits 28 billion pounds."

The shafts in South Africas deepest gold mines are over 12,000 feet deep. Without any kind of air conditioning, the temperature is 95 at 5,000 feet, a 114 at 9,000 feet, and 135 at 12,000 feet. With air conditioning the temperature hovers is about 90, but humidity is a barely unbearable 90 percent. People unaccustomed to it conditions grow faint and weary just standing up. Mine recruits in training for these conditions step up and down on two foot block in a heated room 12 times a minutes for four hours.

The deepest mine in the world in the 1970s was the Western Deep Gold Mine in South Africa. At 12,720 feet deep, it was nine times deeper than the height of the tallest building. The natural temperature was 131F (55C). To keep the workers from burning up special refrigerators were installed. The mine was so deep and pressure was so great that rock sometimes exploded. [Source: Peter White, National Geographic January 1974, ]

To reach to chambers where the ore was extracted miners were raised and lowered on elevators that held 120 men. These same elevators were used to transport 20 ton loads of rock, which was transported to the shafts with buckets and carts.

The mine chambers, or stopes, were slanted at 21 degrees to follow the reefs. There was barely enough room for a miner to sit up let alone move around. Hydraulic jacks and crisscrossed stacks of logs were used to keep the roof from collapsing. To break off the rock, miners used jack hammer-like drills, which they guided with their feet. There were sometimes 30 or more drills going at one time and the noise level ws akin to being locked in a bathroom with an accelerating supersonic jet. If that wasnt enough sometimes boiling hot streams of water burst out of the rocks and the rock itself exploded because of the pressure.

The amalgamation method of refining gold and silver involves exposing crushed ore to mercury, which is attracted to and attaches itself to gold and silver particles. The resulting mercury-gold and mercury-silver amalgamations are separated from the rest of the ore and then heated until the mercury boils away, leaving pure gold or silver. The mercury from this method can very nasty on the environment.

Cupellation is a primitive method of refining gold and silver ore. The ore is heated on a ceramic plate. Some impurities are absorbed; some are burned away, leaving behind the desired precious metal.

When gold ore is brought in to be processed the ore is first broken into softball-size fragments with a steel crusher. Hand sorters discard pieces without gold. The remaining gold-bearing pieces are pulverized into a powder in a rotating cylinder filled with steel balls.

Cyanide can be used instead of mercury to separate the gold from the rock. It added to the slurry of gold ore to release microscopic bits of gold from the rock. After the rock is filtered out of the gold-cyanide solution, zinc is added to bond with and separate the cyanide. The gold is now an impure powder. The gold is then mixed with borax and poured into a cone. The pure gold collects at the bottom of the cone and the impurities float as slag to the top.

In South Africa much of the gold is molded into 27 pound bars stamped with the South African springbok emblem. Many of these bars are stored in the South African Reserve Bank in Pretoria. In 1974 a vault in this bank held 348 metric tons of gold. During one four month period that year when the value of gold shot up 100 percent and the value of the gold in the vault increased from $770 million to $1.4 billion.

The Economist reported: Investing in gold miners carries risks unrelated to the price of the metal. Mergers can flop. As readily recoverable reserves dwindle in stable places such as North America and Australia, miners are forced to operate in more troublesome ones, such as Latin America and Africa. Huge investments can yield disappointing returns if promising mines turn out to contain less glitter than predicted. [Source: The Economist, June 2 2011]

Gold bugs, by definition, bet that the price of gold will go up and up. Miners sometimes do the opposite. Many hedged their wares, selling gold forward to ensure smooth cash flows and to raise money to dig more mines. This may have seemed prudent at the time. But it repelled gold bugs and, as the gold price rose ever higher, it hurt the miners profits, too. Barrick Gold, the worlds biggest gold miner, and AngloGold Ashanti, the third-largest, have both spent billions unwinding hedges over the past couple of years. [Ibid]

Gold bugs are often allergic to other metals. Gold miners are not. Many produce copper, too, since it often sits in the same ore bodies as gold. In April Barrick offered $7.7 billion to trump a Chinese bid for Equinox, an Australian copper miner. The heavy demand in China and short global supply for red gold makes Barricks move look sensible. But gold bugs hated it. Barricks shares fell sharply after the bid was revealed. [Ibid]

Most damaging of all for the marriage between gold bugs and gold miners has been the arrival of a seductive new financial tool. Exchange-traded funds (ETFs), backed by physical gold, offer investors direct exposure to the gold price without any exposure to gold miners themselves. They have become popular: in less than a decade gold ETFs have gone from nothing to holding some 2,200 tonnes of gold---nearly a whole years production. If the world goes to hell, gold bugs will say: I told you so. But if investors ever wake up and notice that the yellow metal is little more useful than tulips, the gold bugs will be burned. The miners, less so. [Ibid]

According to the Economist: Gold and gold-mining shares used to rise and fall in lockstep. Over the past five years, however, the price of gold has trebled while the value of gold miners has merely doubled. Investors in firms that shift, crush and process rocks are more grounded, it seems, than those who invest in bullion. [Source: The Economist, June 2 2011]

As mines age, extracting gold gets harder and costlier. Ores give up less of the metal---average grades have fallen by 30 percent since 1999 according to GFMS, a consultancy. And ore must be hauled up from ever greater depths. Fuel is pricier. So, too, are labour and equipment, since the global minerals boom has driven up demand for miners and drills. A decade ago the average cost of extracting an ounce of gold from the ground stood at a little over $200. In 2010 it hit $857, says GFMS---though this figure depends in part on the gold price. When gold was $200 an ounce, nuggets that cost $800 to extract stayed buried. [Ibid]

Finding new seams to replace depleted ones is becoming harder. Metals Economics Group, a mining consultancy, estimates that in 2002 gold miners spent $500m on exploration. By 2008 they were spending $3 billion but finding much less. All the easy gold has been mined already. [Ibid]

The big gold-mining firms have turned to acquisitions to boost their reserves. Last year Australias Newcrest bought an Aussie rival, Lihir Gold, for $8.7 billion. By value, 31 percent of the mining deals last year involved gold, according to the consulting arm of PwC. Merged firms seek to cut costs, and often end up spending less on exploration than they did separately. That makes it even less likely that they will find much more gold.The worlds miners dug up 2,689 tonnes of gold last year. Granted, that was a record. But, despite the huge surge in investment, it was only a few flakes more than the total output a decade ago. [Ibid]

Thomas Neal wrote in The Times: Beneath a dilapidated shack Frank Ofori leaps casually into the entrance of a crumbling mineshaft that plunges 200ft into the earth. With a torch strapped to his head and three sticks of dynamite in his back pocket he begins a ten-hour shift underground in the Kenyase mine camp, 200 miles (320km) north of Accra, where thousands of prospectors risk their lives in the hope of finding gold. [Source: Thomas Neal, The Times, April 23, 2011]

Mr Ofori skips over the wooden struts holding the makeshift tunnel together and disappears into an abyss. Miners as young as 10 work in the squalid camp, exploited by gangmaster gold dealers who force them to endure back-breaking labour for less than a few pounds a month. Every day they risk suffocation, broken bones and injury from uncontrolled explosions. The camp is reached through a flooded dirt-track carved into the rainforest, a busy thoroughfare crammed with people carrying generators and mining tools in wheelbarrows. [Ibid]

The sprawling shantytown in a clearing appears to be pockmarked by shelling. Workers tread carefully between the craters, that flood in the rainy season. Only decayed logs and sandbags give away where the mine entrances stand. At Kenyase there are no health-and-safety controls. No one wears a hard hat and at least 40 people died here last year. [Ibid]

The camp has sprung up in the past few years. When American company Newmont---one of the worlds largest gold companies---moved in to the area, thousands of prospectors followed. Mr Ofori spent two years digging his mineshaft with only shovels and pickaxes. We usually go down there for ten hours at a time, he said. We take food and water with us. There is a network of tunnels underground, going on for miles. There are hundreds of us down there.Across the site anyone who isnt digging is sifting through gold ore. A mother with a baby strapped to her back looks through discarded rocks for a thin, yellow streak. [Ibid]

Teenage boys have abandoned their schooling to shovel earth into metal basins that girls carry to a clattering machine where the sludge is filtered. Ayishitu Mohammed, 13, spends every day carrying heavy loads on her head through the opencast pit. I would like to be a nurse but I havent finished at school, she said. That will never happen now. [Ibid]

In April 2011, Newmont approved a new gold project in Ghana. The Akyem mine is expected to produce 7.2 million ounces, with an annual output of up to 500,000 ounces. Such an immense undertaking will make Ghana Africas second biggest producer, after South Africa. Although gold accounts for 90 per cent of exports multinationals pay only 3 per cent royalties. [Ibid]

The charity Action Aid said that Ghana lost 700 million between 1990 and 2007 by not making companies to pay the maximum 12 per cent tax they could have required. In 2005 this would have been equivalent to paying off half the countrys debt. Kwame Badassi, a dealer, holds up a lump of rock containing a slither of gold. It has taken a miner two months to find and is worth only 4. It is the big companies who have the biggest gold deposits. We just get the scraps, he said. [Ibid]

Gold mining is very dirty and environmentally-damaging, It has been estimated that creating enough gold for an 18-karat gold ring generates 20 tons of waste. Strip mining can be particularly damaging, tearing up landscapes and fouling rivers and groundwater.

Mining gold always entails some environmental damage. Gold is always found with heavy metals like mercury, cadmium, lead, copper and zinc, and flushing these metals is destructive. Traditional methods for extract gold include smelting and roasting. They produce poisonous gas emissions and toxic chemicals.

When gold mines are played out gold companies leave behind hectares of scarred earth and deposits of arsenic trioxide in underground chambers. Mountains of rock waste left behind is full of mercury and other toxic materials. The tailings are treated with sodium cyanide and the treated again with other chemicals to reduce the concentrations of cyanide.

Large scale gold processing requires lots of water---in some cases million of liters a day. The water is needed to dilute the cyanide that soaks the ore. When mines and processing facilities are located in dry areas obtaining enough water is one of the biggest problems that has to be overcome. Then world's longest water pipeline transports water 350 miles from Perth to the Kalgoorlie gold fields.

Gold mining sometimes soaks up huge amounts of scarce water in deserts or other dry areas. In some places the water is drawn from aquifers and other underground supplies that could take hundreds, even thousands, of years to replenish.

Companies say they use about 10 percent of the water they pump out. About half of the rest goes into settling ponds, where it is expected to sink back into the aquifers. Some remains in artificial lakes. These sometimes have high levels of arsenic and selenium or other metal. Other times the they contain concentrations of materials that are toxic to fish but not humans or contain water that is relatively clean.

Bioleeching is a method in which mineral-eating bacteria are applied to sulfide solution with gold-bearing sulfide ore. The bacteria oxidizes the sulfide leaving behind a solution from which metal can easily be precipitated out the technique has boosted recovery rates and is environmentally-friendly. In Brazil, Australia and South Africa, gold mines use microbes to treat the raw ore before final processing with cyanide.

No Dirty Gold is a campaign, whose participates include Tiffanys and Zales, that promises that gold being sold has been taken without damaging the environment or violating human rights. and offer synthetic or clean Canadian diamonds and recycled gold.

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Global Viewpoint (Christian Science Monitor), Foreign Policy, Wikipedia, BBC, CNN, NBC News, Fox News and various books and other publications.

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gold ore processing | sciencedirect

gold ore processing | sciencedirect

Gold Ore Processing: Project Development and Operations, Second Edition, brings together all the technical aspects relevant to modern gold ore processing, offering a practical perspective that is vital to the successful and responsible development, operation, and closure of any gold ore processing operation. This completely updated edition features coverage of established, newly implemented, and emerging technologies; updated case studies; and additional topics, including automated mineralogy and geometallurgy, cyanide code compliance, recovery of gold from e-waste, handling of gaseous emissions, mercury and arsenic, emerging non-cyanide leaching systems, hydro re-mining, water management, solidliquid separation, and treatment of challenging ores such as double refractory carbonaceous sulfides. Outlining best practices in gold processing from a variety of perspectives, Gold Ore Processing: Project Development and Operations is a must-have reference for anyone working in the gold industry, including metallurgists, geologists, chemists, mining engineers, and many others.

Gold Ore Processing: Project Development and Operations, Second Edition, brings together all the technical aspects relevant to modern gold ore processing, offering a practical perspective that is vital to the successful and responsible development, operation, and closure of any gold ore processing operation. This completely updated edition features coverage of established, newly implemented, and emerging technologies; updated case studies; and additional topics, including automated mineralogy and geometallurgy, cyanide code compliance, recovery of gold from e-waste, handling of gaseous emissions, mercury and arsenic, emerging non-cyanide leaching systems, hydro re-mining, water management, solidliquid separation, and treatment of challenging ores such as double refractory carbonaceous sulfides. Outlining best practices in gold processing from a variety of perspectives, Gold Ore Processing: Project Development and Operations is a must-have reference for anyone working in the gold industry, including metallurgists, geologists, chemists, mining engineers, and many others.

gold processing 101 - mining magazine

gold processing 101 - mining magazine

Amidst the general fall in metal prices over the last few years, the gold price has remained comparatively stable in the US$1,000-1,250/oz range. Gold bulls were disappointed that the price did not break through the $2,000/oz ceiling; nevertheless the current stable price run has helped to maintain a strong interest in gold projects.

The second is the sustained, and dare I say sustainable, use of cyanide for gold leaching in the last 100 years or more in a world of increasing environmental concerns and general aversion to the use of toxic chemical like cyanide. Alternatives to cyanide are not the subject of this article, but it is suffice to say that recent applications of alternatives to cyanide, e.g. thiosulfate at Goldstrike Nevada, have been driven by technical rather than environmental imperatives. In the case of Goldstrike, this was a double-refractory ore combining sulphide-occluded gold with preg-robbing carbonaceous material that rendered the ore unsuitable for conventional cyanide leaching and carbon adsorption.

In most cases, gold processing with cyanide leaching, usually with carbon adsorption, is still the core technology and the critical thing is understanding the mineralogy in order to optimise flowsheet selection and cost drivers, and get the best out of the process.

Traditionally, the process selection choice was between a conventional, well-tried, three-stage crushing circuit followed by ball milling, or single-stage crushing followed by a semi-autogenous (SAG) mill and ball mill. The latter is preferred for wet sticky ores to minimise transfer point chute blockages, and can offer savings in both capital costs and long-term operating and maintenance costs. However, the SAG route is more power-intensive and, for very hard ores, comes with some process risk in predicting performance.

Now that initial wear issues have largely been overcome, they offer significant advantages over a SAG mill route where power costs are high and the ore is very hard. They can be attractive too in a heap leach where the micro-cracking induced by the high pressure has been demonstrated in many cases to improve heap leach recovery.

The hashing stage (corresponding to metal extraction and recovery stages) is a little more complex for gold ores, as the optimal process flowsheet selection choice is heavily dependent on a good understanding of two fundamental geometallurgical parameters, the gold mineralogical associations, and the gold particle size and liberation characteristics. These are summarised in Table 2, where the processing options that correspond to the various combinations of mineral associations and liberation are shown along with some examples.

This is common in tropical environments (e.g. West Africa) and typically oxidises gold-bearing sulphides down to 50-100m, transforming commonly refractory gold in sulphides to free-milling gold, behaving in a similar fashion to gold associated with quartz.

Refractory ores are typically treated by flotation and the resulting flotation concentrate may be sold directly to a smelter (common for example in China) or subjected to downstream processing by pressure oxidation or bio-leach.

An ore containing 1% sulphur will produce a mass pull of approximately 5% by weight to a bulk flotation concentrate where recovery is the key driver. If this ore also contains 1g/t Au (for GSR =1), and 90% recovery to concentrate is achieved, then 0.90g will be recovered and with a concentration ratio of 20 (5% to concentrate) this corresponds to 18g/t Au in concentrate.

Both smelter treatment charges and oxidation or bio-leach costs are at least $200/t of concentrate and payables/recovery in the 90% range, so a minimum GSR for effective downstream processing is around 0.5. Clearly this is a function of gold price, but in the current gold price and cost environment, a good rule of thumb is that a minimum GSR of 0.5 is required for downstream processing of a gold-bearing concentrate.

A lower GSR can be tolerated if the flotation concentrate is amenable to direct cyanide leaching without the costly oxidation stage to release the gold from the sulphides. And on-site dor production avoids the off-site costs of transport and smelter charges, but usually with lower recovery (flotation recovery then oxidation-leach recovery) so a trade-off analysis is required.

Smelters typically pay >95% (Au) and 90% (Ag) in copper and lead concentrates, but will only pay 60-70% (maximum, depending on degree of Pb/Zn smelter integration) for gold and silver in zinc concentrates.

It can be seen that the key cost elements are: power, cyanide and grinding steel plus, for refractory ores, the costs associated with pressure oxidation or bio-leaching. It should also be noted that, where cyanide destruction is required (increasingly the norm), then cyanide detox unit costs are usually of a similar order of magnitude to the cyanide unit cost.

In summary, and of particular relevance to project screening, an early appreciation of gold mineralogical associations and liberation can provide considerable insight into metallurgical process flowsheet selection and processing costs.

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gold processing,extraction,smelting plant design, equipment for sale | prominer (shanghai) mining technology co.,ltd

gold processing,extraction,smelting plant design, equipment for sale | prominer (shanghai) mining technology co.,ltd

Prominer maintains a team of senior gold processing engineers with expertise and global experience. These gold professionals are specifically in gold processing through various beneficiation technologies, for gold ore of different characteristics, such as flotation, cyanide leaching, gravity separation, etc., to achieve the processing plant of optimal and cost-efficient process designs.

Based on abundant experiences on gold mining project, Prominer helps clients to get higher yield & recovery rate with lower running cost and pays more attention on environmental protection. Prominer supplies customized solution for different types of gold ore. General processing technologies for gold ore are summarized as below:

For alluvial gold, also called sand gold, gravel gold, placer gold or river gold, gravity separation is suitable. This type of gold contains mainly free gold blended with the sand. Under this circumstance, the technology is to wash away the mud and sieve out the big size stone first with the trommel screen, and then using centrifugal concentrator, shaking table as well as gold carpet to separate the free gold from the stone sands.

CIL is mainly for processing the oxide type gold ore if the recovery rate is not high or much gold is still left by using otation and/ or gravity circuits. Slurry, containing uncovered gold from primary circuits, is pumped directly to the thickener to adjust the slurry density. Then it is pumped to leaching plant and dissolved in aerated sodium cyanide solution. The solubilized gold is simultaneously adsorbed directly into coarse granules of activated carbon, and it is called Carbon-In-Leaching process (CIL).

Heap leaching is always the first choice to process low grade ore easy to leaching. Based on the leaching test, the gold ore will be crushed to the determined particle size and then sent to the dump area. If the content of clay and solid is high, to improve the leaching efficiency, the agglomeration shall be considered. By using the cement, lime and cyanide solution, the small particles would be stuck to big lumps. It makes the cyanide solution much easier penetrating and heap more stable. After sufficient leaching, the pregnant solution will be pumped to the carbon adsorption column for catching the free gold. The barren liquid will be pumped to the cyanide solution pond for recycle usage.

The loaded carbon is treated at high temperature to elute the adsorbed gold into the solution once again. The gold-rich eluate is fed into an electrowinning circuit where gold and other metals are plated onto cathodes of steel wool. The loaded steel wool is pretreated by calcination before mixing with uxes and melting. Finally, the melt is poured into a cascade of molds where gold is separated from the slag to gold bullion.

Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.

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