How gold is mined, found and processed in the world today (12 photos)

What if you are a born prospector and the romance of modern treasure hunting is not alien to you?

It's not too late to leave the dusty office and go looking for gold in search of new deposits.





What gold looks like in nature

This metal is present practically everywhere: in living organisms, soil, water, but in minute proportions. In deposits it is found in the form of nuggets, sand, thin veins and inclusions in the rock from noticeable to microscopic particles, indistinguishable without powerful optical instruments.



Chemical and physical properties

This is the first metal that humanity mastered. The substance is bright yellow in color, does not oxidize in air and water, and is inert towards most known acids and alkalis, for which it is called a noble element. It dissolves in concentrated perchloric acid. The famous aqua regia - a solution of hydrogen chloride with nitric acid - is widely used by jewelers as a gold solvent. It also reacts quite easily with a concentrated aqueous solution of bromine, fluorine, and cyanide. Forms an intermetallic compound with mercury in the form of a low-melting alloy (amalgam).

The physical properties of this substance are unusual - it is one of the rarest and heaviest (Au is 7th place in the periodic table) metals in the earth's crust. A cubic centimeter of pure gold weighs more than 19 grams. At the same time, the substance is very soft and plastic. It can be crushed with your fingers, rolled into a sheet 100 nanometers thick, and 1 gram can be stretched into the thinnest wire more than 2.5 km long.

The process of gold formation in nature

Scientists have not found agreement on the origin of this metal. The latest version is the explosion of a neutron star, after which dust formed consisting of heavy elements. It condensed and served as the basis for the emergence of the core of our planet, where the bulk of gold reserves are currently concentrated.

The metal that is found on the surface presumably got there during the heavy bombardment of the planet by meteorites or as a result of volcanic activity along with the eruption of magma.

How are gold veins found?

Previously, discoveries of new deposits were often random. A curious man in the street, attracted by the unusual golden color of grains of river sand or the suspicious weight of a stone, picked up an intriguing object, which turned out to be a nugget.





There is a known case where for decades a family in Siberia used a massive black cobblestone as a pressure when pickling cabbage, until a casual acquaintance with experience as a prospector recognized it as a huge nugget.

The first deposit was discovered by dissenter Erofei Markov, who found a nugget on the road and brought it to the factory office in Yekaterinburg.

Satellites of gold

This element is never found in nature in its pure form. The most common form is sulfides and arsenides. A total of 15 associated minerals are known - silver, rhodium, iridium, platinum, bismuth, copper and others.

Where is gold found in nature?

Nowadays, enough information has been collected about where deposits are most often found, which allows us to use a scientific approach in the search for gold-bearing veins. On an industrial scale, post-magmatic hydrothermal formations are of greatest interest, where there is a high probability of the presence of a placer deposit. In late portions of granitic magmatic melts, gold is also found in the form of inclusions. The mountain ranges are rich in this metal - the Urals, the Cordillera, the Andes.

Research in recent years has shown that bacteria can also accumulate gold in their cells. In the deposits of Kamchatka, Benin and South Africa, golden bacteria were found - particles of metal in the form of chains characteristic of these microorganisms, as well as the remains of armored growths of unicellular colonial algae and their cysts.

Some types of protozoan microorganisms are able to dissolve this metal, turning it into a bioavailable substance for other plants and animals.

Types of gold deposits

Based on the principle of formation, gold deposits are divided into endogenous (primary) and exogenous (secondary). The type of deposit does not affect its richness, location or physico-chemical composition of the gold ore.

Primary, or ore, deposits. Primary, or indigenous, include ore deposits in areas where granitoids occur. Mining at such mines is a more labor-intensive process and is carried out using the shaft method. The development of such deposits began in the 20th century.

Eluvial deposit. Belongs to the exogenous, or secondary, type. It is formed in places where the primary source emerges due to its destruction (weathering, erosion, leaching) and contains precious metal only a few tens of meters from the primary deposit. By looking at its gold content, you can get an idea of ​​how high the metal content is in the rock.

Colluvial placer. Also a deposit of exogenous nature. Under the influence of natural factors, the elements of eluvium (large pieces of rock) are destroyed even more, grains of native gold contained in the ore are released and washed away by water, settling as sand deposits on the slopes and in depressions of the relief. The source of such a deposit is both one powerful primary and several poor deposits. The placer may be located on the surface or hidden by a layer of waste rock.

Extraction methods

The development of modern technologies has allowed gold mining companies to increase the profitability of production and obtain gold from previously mined soil. But along with new technologies, long-known methods are still widely used.

How gold was mined in the old days

At the dawn of civilization, gold mining was limited to finding large enough nuggets from which jewelry was made. The oldest object found in Bulgaria and resembling a hairpin was made 6 thousand years ago.

artisanal

Later, they began to use the method of washing the soil with water, which made it possible to extract not only large nuggets, but also fine sand. The first miners used a gold pan as their main tool. The heavy metal settled at the bottom, and the lighter soil was carried away by the flow of water. This painstaking method is still used by “wild” prospectors to sift previously spent rock in abandoned deposits.



Transmutation

In the Middle Ages there was such a science as alchemy. It consisted of searching for the philosopher's stone, with the help of which it was supposedly possible to turn lead and copper into gold. Even the famous Newton spent three decades researching this method.

The first successful transmutation was carried out in March 1947 - artificial gold was formed from mercury isotopes in a nuclear reactor. This led to a collapse in stock exchange prices, but the panic did not last long. The cost of the precious metal obtained artificially was several times higher than the samples mined even from the poorest mines, and this method did not have any economic potential other than scientific interest.



Of the breed

To extract gold from rock, it was necessary to first crush it for further washing. This method had low efficiency. However, in 1843 engineer P.R. Bagration proposed an option for extracting gold from ore by treating it with a cyanide solution, which significantly increased the volume of gold mining from ore deposits.



In sea water

Sea water can serve as a source of precious metal. Its concentration in liquid is small - no more than 0.16 g per ton, but on a global scale it is more than 25 million tons. For comparison: throughout the history of gold mining, humanity has received about 160 thousand tons of the precious metal.



Wastewater

In 1977, a method for extracting precious metals from wastewater was patented. The process included several stages: bacterial treatment to separate the sludge, its drying, combustion and exposure of the resulting ash to acids. The developer of the method, Markels, managed to achieve the separation of 90% of the gold contained in industrial and domestic wastewater. Processing 102 thousand cubic meters of wastewater yielded up to 164 grams of gold. The result was worse than expected and did not cover the costs.



From sand

Even ordinary sand on the bank of the nearest river probably contains some amount of the precious metal. Its volumes may not be enough to organize full-fledged mining on an industrial scale, but as an experiment or hobby, manually panning and obtaining a small amount of gold at home is a completely feasible undertaking.



Industrial gold mining technologies

Modern gold mining on an industrial scale, comparable to market needs, requires the use of advanced technologies. This makes it possible to increase the profitability of even those fields that were previously considered unpromising. Depending on the type of mine, two methods of its development are used.

Open way

The open, or quarry, method is used in the development of secondary or alluvial deposits. It is less expensive, since the gold-bearing rock is located on the surface and does not require crushing. The work is carried out in the warm season, but winter mining has its advantages - better accessibility to promising places hidden under water in the summer and water transparency, which provides a better visual overview of the sandy bottom.

Gold is extracted from sand by panning. Under the pressure of water, gold-bearing sand moves along special gutters with a relief bottom (dredges). The waste rock is washed away, and the gold, due to its mass, gets stuck in the depressions, after which it is collected and sent for further processing.



This extraction method has its advantages and disadvantages. The positive point is simplicity and low cost. The negative side is low efficiency. There is a high probability of missing large nuggets that are not stuck in the small cells of the dredge. To avoid such cases, the employee on duty carries out visual control of the process.

Closed method

The closed (mine) mining method is necessary when developing primary or primary deposits, when the gold-bearing vein goes deep underground. This method requires more complex and expensive equipment, blasting and processing of ore using various chemicals.

Amalgamation

The technique is based on the ability of gold to react with mercury. The crushed rock is moistened with mercury with the addition of lime, the resulting amalgam is separated from the ore, filtered and evaporated, releasing the gold. After this, the mercury is reused, and the noble metal, purified to 75–90% purity, is ready for further processing.

The method was known 2 thousand years ago and was widely used earlier. However, it is associated with a high degree of environmental pollution and is not effective enough. The degree of gold recovery is 50–70% of the total content. Also, the method cannot be applied if there are sulfides in the rock.

It is used primarily for secondary processing of rock after washing.

Heap leaching

The most common technique, now used in all fields. The gold ore is placed on a waterproof surface and treated with an aqueous solution of sodium cyanide. The resulting liquid is collected, the precious metal is precipitated using reagents and undergoes further purification.

What happens next to the mined gold?

The mined metal still contains impurities. They are removed using refining. At the initial stage, the raw material is cleared of iron impurities and treated with nitric acid, while gold precipitates. Further processing is carried out using hydrochloric and nitric acids and evaporation. This method allows you to achieve a purity of the substance at the level of 99.95%.



To achieve maximum metal purity, electrochemical refining is used: hydrochloric acid in solution serves as an electrolyte, the anode is the raw material for purification, and the cathode is a rod of gold of the highest standard.

Use of precious metal in various industries

The main industries in which this metal is widely used are:

jewelry industry;

creation of modern electrical appliances;

optics;

medicine;

cooking;

atomic research;

production of weapons of mass destruction.

Only a tenth of the extracted noble element goes into industry, about 45% ends up in the gold and foreign exchange reserves of states and private individuals. The rest of the metal is used to make jewelry.

History of the development of gold-bearing veins

Archaeologists suggest that gold mining as a branch of the national economy originated in the Middle East. From there, jewelry was exported to Egypt. The first finds in Sumerian tombs are more than 3 thousand years old.

One of the richest cultures in gold reserves was the ancient Inca Empire, which was located in the territory of modern Mexico, Peru and Chile. Their legacy is the mythical golden city of Eldorado, in search of which the Spanish conquistadors went.

In the 15th century, the first deposits were discovered in Mexico, Chile and Ghana. Three centuries later, the first gold mining cooperatives appeared. In 1823, the richest veins were discovered in Canada and America, which was marked by the outbreak of the famous “gold rush”. Even later, deposits were discovered in South Africa and Australia.

Gold mining in the world today

Today, the total production of gold in the world is more than 2.5 thousand tons annually. The last financial crisis of 2008 significantly activated the growth of gold reserves in many countries. Accumulation in gold is an effective measure to protect the state from the consequences of stock exchange crashes, the result of criminal fraud in the Central Bank market.

Leading countries in gold mining

Among the states that have gold deposits and are developing them in 2017, the leaders are:

China - 440 tons;

Australia - 300 tons;

United States - 230 tons;

Canada - 175 tons;

Peru – 160 tons;

Indonesia - 155 tons;

South Africa - 145 tons;

Mexico - 130 tons;

Ghana – 100 tons.

Famous gold deposits

An interesting fact is that 90% of all gold production in the world is provided by the ten largest deposits. The richest and most famous include:

Muruntau, Uzbekistan. According to preliminary estimates, it is 2.5 times more promising than the next field on the list.

Grassberg, Indonesia.

Pueblo Viejo, Dominican Republic.

Yanacocha in the Cajamarca region, Peru.

Carlin Trend, Nevada, USA.

Goldstrike mine, which includes 3 deposits, USA.

Cortez, Nevada, USA.

Veladero mine in Argentina.

Boddington Quarry, Australia.