How are diamonds mined? How are diamonds mined? Without a cut you are glass, but with a cut you are a million

How are diamonds mined?

Diamond is considered to be the hardest natural mineral of all known, molecularly a form of carbon. Among precious stones, the diamond firmly occupies one of the most important places, and cut diamonds, or diamonds, are considered the most important jewelry. How are diamonds mined?

Nature and deposits of diamonds

By its nature, diamond is a very hard dielectric, which has high wear resistance and elasticity, as well as the ability to luminesce. The overwhelming majority of diamonds are yellow or brown, but pink, green, blue and even red diamonds are also found in nature (there are about 10 such diamonds in the world). Diamonds are used in the manufacture of drills and cutters, in the nuclear industry, as well as in the production of microelectronics for computers and watches.

Before you can understand how a diamond is made, you need to know the nature of the formation of these gemstones. Modern scientists adhere to the mantle theory of the origin of diamonds, according to which carbon atoms are formed into a diamond crystal lattice under high pressure underground at a depth of more than 200 km. Subsequently, such diamond rocks are pushed by volcanic magma to the surface of the earth in so-called “explosion tubes.” In addition, these precious stones are found in river placers, therefore in the mining industry such diamond deposits are considered to be a secondary type of diamond deposit.

Initially, diamonds were mined for many centuries from placers in India in the legendary Golconda mines, but by the 18th century, Indian diamond deposits were depleted. Since 1725, Brazil became the main diamond-mining country, supplying high-quality diamond crystals from an extensive network of river placers. But 150 years later, diamond mining changed dramatically thanks to the discovery of the first “explosion tube” in 1867 in South Africa in the town of Kimberley. That is why later diamond deposits began to be called kimberlite pipes, and the modern diamond mining industry is entirely built on the extraction of diamonds from kimberlite and lamproite pipes.

Now there are about 35 diamond-mining countries in the world, among which Botswana, Russia, Canada, and South Africa are considered the leading ones. Angola and Namibia. In Russia, the richest diamond deposits are considered to be in Yakutia, the Arkhangelsk region and the Perm region.

Stages of diamond mining

Diamond mining is considered a very costly and complex process, which initially requires large financial investments. In order to understand how diamonds are mined, you need to consider all the stages of organizing diamond mining from start to finish:

• Exploration stage. It takes more than one year, and sometimes even a decade, to first find a diamond deposit and extract its first specimen, confirming the deposits of the precious stone in this particular territory.
• Infrastructure stage. After confirmation of diamond reserves, a site is prepared where the stone will be mined, machinery and all necessary equipment are purchased, and a residential infrastructure is created for people who will mine and process the stone. So, to prepare the site, the following methods are used:
  • if a kimberlite pipe lies on the ocean floor, then subsequent diamond mining will be carried out using special robots equipped with electronic control, which, when extracting rock, immediately find precious stones and pack them in closed containers;
  • If the kimberlite pipe is located deep underground, then diamond mining is carried out using closed underground mines, which is considered an extremely dangerous and complex diamond production that requires even greater investments.
• Factory stage. As soon as all the necessary infrastructure has been created, the construction of a processing plant begins, where diamonds will be extracted from the rock. In addition, management is recruiting personnel who will service all stages of the diamond mining process.
• Mining stage. This stage is considered both final and beginning, because it is here that the entire production from mining to diamond processing starts. How are diamonds mined at this stage? According to common diamond mining and processing technology, the entire process consists of the following stages:
  • primary crushing of ore to volumes of 50-150 mm, sifting and sorting of ore into diamond kimberlite and accompanying rock (this stage is carried out at the mine itself using special mobile units);
  • secondary crushing of ore to volumes of 1-32 mm, sifting, sorting of ore into 4 categories of pure diamond kimberlite (1-4 mm, 4-8 mm, 8-16 mm, 16-32 mm) and separating it from associated rocks (this stage takes place in a factory);
  • sending to the sorting shop, where, using special technology, the final inspection and selection of diamonds by diameter, class and weight takes place.
• Typically, once the sorting process is completed, the diamonds recovered using various techniques become traded items.

Diamond mining technologies

• How do you get a diamond? Among modern technologies for separating and sorting diamonds, the following are especially popular:
• Use of fat installations. Fat installations are considered quite primitive, since when sorting diamonds, tables covered with a layer of fat are used, onto which diamond kimberlite mixed with water is released. As a result, the rock is carried away along with the water, and the diamonds stuck to the fatty surface are collected by hand.
• Use of X-ray units. X-ray machines are considered more advanced because when the ore is irradiated, the diamonds begin to glow blue, which activates a pneumatic pusher that automatically cuts off the precious stones.
• Use of electromagnetic installations. Since diamond is practically not attracted by magnets, and the rock in which it is found, on the contrary, has a significant degree of magnetic radiation, using electromagnetic installations, precious stones are easily separated from the rock ore.
• Use of suspension plants. This method is used to extract precious stones from diamond deposits by placing diamond-containing rock in a high-density liquid (ferrosilicon). In this case, heavy stones sink to the bottom, and light ones remain on the surface and subsequently go through the enrichment stage.
• Using units with foam flotation units. This method is used in the production of diamond dust, when diamond-containing rock is processed in workshops with millstones. Since kimberlite has a lower hardness, the resulting diamond dust is extracted using an installation with a foam flotator.

To date, diamonds have been found on all continents of the Earth, including in Antarctica, where fragments of an iron meteorite with diamonds were discovered. Natural diamonds are estimated to be over 100 million years old.

Diamond is one of the most important and valuable minerals. Diamond deposits are divided into two large groups: bedrock (primary), associated with igneous rocks, and alluvial (secondary), which arose from the destruction of bedrock deposits. Primary diamond deposits are kimberlites and lamproites; all over the world they are confined to ancient platforms - Indian, Chinese, Siberian, East European, Australian. The following geological and genetic types can be distinguished from placers, the sources of which can be objects of profitable diamond mining: deluvial, proluvial, alluvial and marine (coastal and shelf).

Initially, diamonds were found only in placers and almost always by accident. Speculation has been made about the indigenous sources of this mineral, but no one has undertaken a systematic and targeted search for it. Only after the discovery of the first diamonds in the river sediments of South Africa, prospectors unexpectedly stumbled upon their accumulations far from the rivers. They did not suspect that they were dealing with bedrock deposits of diamond-bearing rock and simply called them “dry diamond mines” in contrast to the “wet mines” located in river beds. The first dry mine was discovered in 1870 and named Jagersfontein. In the same year and the following, other mines were found, including the Colesberg mine, or New Rush, renamed Kimberley in 1873.

But the first primary diamond deposits were not found in Africa. Scientists have proven that the first primary diamond deposit was found in India long before the discovery of South African kimberlites. Thus, at present, the oldest active primary diamond deposits are Indian, but, according to some estimates, only about 15 thousand carats are mined there annually.

The approximate distribution of diamond resources between primary sources and placers is 85% and 15%, respectively, so the most important sources of industrial diamond mining are kimberlite and lamproite pipes. They are called pipes because the diamond-bearing rock is concentrated in a volume resembling a cone-shaped tube.

Kimberlite pipe - primary diamond deposit

A kimberlite pipe is a gigantic column ending in a conical bulge at the top. With depth, the conical body narrows, resembling a giant carrot in shape, and at some depth it turns into a vein. Kimberlite pipes are unique ancient volcanoes, the ground part of which is largely destroyed as a result of erosion processes. One of the largest diamond-bearing pipes is located in Tanzania - the Mwadui mine pipe. It occupies an area more than 2.5 km long and more than 1.5 km wide. Kimberlite is an ultrabasic rock of brecciated structure, which consists of olivine, phlogopite, pyrope and other minerals. It has a black color with bluish and greenish tints. Currently, over 1,500 kimberlite bodies are known, of which 8-10% are diamond-bearing rocks.

According to experts, about 90% of diamond reserves from primary sources are concentrated in kimberlite pipes, and about 10% in lamproite pipes.

Diamond-bearing lamproite was first discovered in Australia in 1976. This is a different genetic type of diamond deposits from kimberlites. Lamproites are geographically related to kimberlites; the composition of both has much in common, but there are also significant differences. Lamproite differs from kimberlite in its high concentration of titanium, potassium, phosphorus and some other elements. At the same time, there are no significant differences between diamonds of these two types of magmatites. The Argyle pipe deposit contains the largest diamond reserves in the world. Only about 5% of lamproite diamonds can be used in the jewelry industry, the rest are used for technical purposes. The Argyle pipe is the main source of rare pink diamonds. In addition to Australia, lamproites are known in Brazil, in our country - Karelia and the Kola Peninsula.

There is a peculiarity in the location of primary diamond deposits - they are confined to hard-to-reach uninhabited territories. If from these positions we consider the location of almost all currently known diamond-bearing kimberlite and lamproite pipes, we get the following picture. The first diamond-bearing kimberlite pipes in South Africa were discovered in its central part, where until the 70s of the 19th century only a few drill colonists tried to develop the African bush for agricultural land. There were no substantial settlements in these areas at that time. The cities of Kimberley and Johannesburg arose later: the first after the start of the development of diamond deposits, the second - near the largest gold mine. In Lesotho, nature has hidden kimberlites high in the mountains, which can only be reached on foot or on horseback. The diamond-bearing kimberlites of this country are called the highest in the world. The kimberlite pipes of Botswana (Orapa and Jwaneng) - the largest in the world - are located in the waterless, hot Kalahari Desert, where they are also covered with many meters of sand. The same applies to the diamond deposits of other African countries - Tanzania, Guinea, Angola, Sierra Leone, Mali, etc.

A few outcrops of diamond-bearing kimberlites in India are localized within the desert territory of the state. Madhya Pradesh and other states. Even in such an overpopulated country as China, diamond-bearing kimberlites are located in relatively uninhabited places.

Diamond-bearing kimberlites are concentrated in the northern hemisphere under particularly unfavorable climatic and geographical conditions. Yakutia is a permafrost territory, Arkhangelsk is a swampy taiga, low temperatures in winter. Canada's diamond fields are located in the north of the American continent, in an area where there were no settlements or any infrastructure. In addition, 75% of kimberlite bodies there are located under lakes.

Placer diamond deposits are formed mainly due to the erosion of bedrock kimberlite pipes. Placers are located near primary deposits within kimberlite areas and fields or arise at a distance from these areas in geological and structural conditions favorable for placer formation, creating independent diamond-bearing placer areas and fields. At the same time, the morphology of the crystals changes, their differentiation by size occurs, etc. Due to the fact that diamond has a special abrasive resistance, it can be transported over long distances from the root source, sometimes thousands of kilometers (for example, coastal-marine placers of South-West Africa) . If we consider the entire set of crystals and their intergrowths located in the root source of abrasive resistance, then during transportation their unstable part is destroyed. Therefore, diamonds from placers, even those located close to the primary source, are superior in quality to diamonds from kimberlites of this pipe. In the process of even short transfer, some of the joints and stones with various defects are destroyed, which leads to an increase in the share of jewelry diamonds.

Diamond mining is a costly process that requires expensive equipment and modern technologies. But these nuggets are worth it, as they are the most precious stones in the world.

Diamond deposit

Diamond is the hardest mineral whose chemical composition is based on carbon. Diamond is a good dielectric, has high wear resistance and the ability to glow. Most often, minerals are found in yellow or brown, but in nature there are pink, green, blue and red nuggets.

These mysterious and wonderful stones are formed as a result of high pressure and temperature in the bowels of the earth at a depth of about 400 m. Precious particles reach the surface along with erupted magma during volcanic eruptions. In this way, primary deposits of valuable minerals are obtained, which are called kimberlite pipes.

Secondary deposits of stones are placers that are formed during soil erosion. In this case, stones are washed out from primary deposits and end up on the coastal bottom of rivers and seas.

Nuggets were first discovered in the 9th century BC. in India. Mining of stones was carried out in this country until the 18th century, until the diamond deposits were completely depleted. Currently, the leading positions in jewelry mining are occupied by Brazil and the countries of South Africa.

The largest countries that participate in world diamond mining:

• Botswana;
• Angola;
• Russia;
• Congo;
• Namibia;
• Guinea;
• Ghana;
• Republic of South Africa.

A small accumulation of kimberlite rocks is found in the Arctic Circle, the Sahara Desert, Australia, Canada and the countries of the Far East. In total, there are about 35 countries that mine jewelry.

Based on the results of 2007-2008. Russia ranked first in terms of mineral production. The first nuggets were found in 1829 in the Urals, but industrial mining has been carried out in our country since 1954. The Zarnitsa kimberlite pipe is the first primary deposit in the USSR. Currently, diamond mining is widely carried out in the following regions: the Republic of Sakha, Perm and Arkhangelsk regions.

Until the end of the 19th century, diamond mining was carried out by open-pit mining. Quarries on kimberlite pipes reached very great depths, which posed a danger to the process itself. Later, kimberlite pipes began to be developed using a combined method: the upper part of the safe depth - open pit; and the lower part - underground. The underground method is more complex.

Global mineral production has increased severalfold since 1980, but gemstones are still considered scarce. This is due to high labor intensity, expensive equipment and significant labor and time resources.

There are approximately 12,000 diamond deposits found worldwide, of which only 1% contain enough diamonds to justify the mining process economically.

To extract a precious mineral weighing 1 carat, you need to process 1 ton of rock!

How are diamonds mined?

This process consists of the following main stages:

1. Intelligence service.
2. Preparation of the site and necessary equipment.
3. Construction of a factory.
4. Mining stones.

It takes more than one year and even more than one decade to discover the location of diamonds.

As soon as diagnostics have confirmed mineral deposits in a particular area, experts begin:

• prepare the site where the stones will be processed;
• purchase equipment;
• develop infrastructure for workers and other people involved in the process.

Technological equipment depends on the method of stone extraction. If a kimberlite pipe lies on the ocean floor, then the extraction of precious stones will be carried out using electronically controlled robots. Robots extract rocks that contain diamonds and pack them into containers.

If the kimberlite pipe is underground, the minerals are mined through closed underground mines. This method is expensive and complex.

Construction of the factory begins when all the infrastructure is ready. At this plant, precious stones are extracted from rocks and the minerals are further processed.

The extraction of diamonds and their processing has a certain technology:

1. First, the ore is initially crushed to 50-150 mm.
2. This mixture is sifted and sorted into diamond kimberlite and other accompanying rock. This process is carried out at the mine itself using special installations.
3. Next, the ore is secondary crushed to 1-32 mm, which is then sifted and sorted into 4 categories. Diamonds in their pure form are sorted by particle size: 1-4 mm; 4-8 mm; 8-16 mm; 16-32 mm. Sorting of pure mineral, as well as separation of accompanying impurities, is carried out at the factory.
4. The final stage is sending the diamonds to the sorting shop, where the final inspection and selection of stones by size, weight and class is carried out.

The processed stones are sent to the world jewelry trading market.

Methods for separating diamonds from rocks

Extracting small diamond stones from rocks by sifting is an inefficient and labor-intensive process. To understand how diamonds are mined, you need to consider several technologies that separate jewelry from the general mass of rocks. So, there are the following methods for obtaining precious particles:

1. Fat installations. This equipment consists of special tables covered with fat. Diamond kimberlite diluted in water is poured onto these surfaces. As a result, the precious stones stick to the table, and the rock along with the water is carried away. Adhering particles are then collected manually. This is considered a primitive method of mining nuggets.
2. X-ray installations. The essence of the method is that the rock ore is irradiated with X-rays, and the diamond particles begin to glow blue. A pneumatic pusher is automatically activated, which cuts off precious minerals from the total mass.
3. Electromagnetic equipment. This technology is based on the fact that diamonds are practically not attracted by a magnet, unlike particles of rock that contain jewelry. Therefore, the magnet attracts the elements of the rock, and the diamonds themselves are eliminated from it.
4. Suspension plants. Using this method, precious stones are extracted from diamond placers by lowering the rock mass into a high-density liquid - ferrosilicon. As a result, heavy particles sink to the bottom, and light fractions of diamonds remain on the surface.
5. Using a foam flotator. This method is used to separate diamond dust that is generated in processing shops. The essence of the method is that diamond particles with lower hardness are extracted using an installation with a foam flotator.

Diamond mining is widespread throughout the world, and the demand for stones is constantly growing.

Diamonds are one of the most valuable rocks on the planet. Found in several regions, it is mined in a variety of ways. People of many professions, from geologist to jeweler, work to make a diamond a diamond.

For diamond crystals to appear, the following conditions are necessary:

1. Depth from 100 km.
2. Temperature not lower than 1100°C.
3. Pressure of at least 35 kilobars.

Natural processes create types of deposits:

• Indigenous. Diamonds were carried upward by the flow of magma during volcanic eruptions. Gas bubbles in the rock burst, forming tubes with dark bluish rock inside. It was called kimberlite, and the diamond-bearing pipes were called kimberlite, after the place of its first discovery - the South African province of Kimberley.
• Loose. Over thousands of years, the air destroyed the tubes. Precipitation and streams washed away crushed stone, pebbles, and diamonds from the mountains, creating placer fields.
• Impact. Appeared at the sites of meteorite impacts.

There are thousands of tubes scattered around the world, but few are suitable for industrial development. The rarest meteorite diamonds are left for scientists to study.

Technological cycle

Diamond mining is a project that requires financial investment. Funds are needed for geological exploration, equipment, construction of a processing plant, payment of workers, and preparation of deposits.

The technology of work involves the following stages:

• Geological exploration. It takes months or years. When precious crystals are discovered, calculations are carried out to confirm that this is a solid deposit and not isolated finds.
• Purchase of equipment. They are not mined by hand; they need equipment to set up the mine and transport to move the rock.
• Creation of infrastructure. The field employs people who need somewhere to live, eat, and receive treatment. Often a mine becomes a city-forming enterprise.
• Construction of a factory. Selling raw materials is unprofitable, so a beneficiation plant is built, where precious stones are separated from the rock, sorted and sent to a cutting plant. Here the material will be processed, cut and polished.

The deeper the rock lies, the more substantial the investment. To obtain one carat, a ton of mine rock is processed. Placers are more generous - a ton of rock yields from three to five carats.

Extraction methods

Until the 19th century, diamonds were mined with a shovel, raking river sand and washing the rock on trays. Today the process is mechanized, the extraction methods are mine and quarry (open pit). How diamonds are mined depends on the depth of the rock.

Career

Diamonds concentrated no deeper than 600 m are mined in quarries. They drill holes into which explosives are placed. They blow it up and load dump trucks with the ejected rock on their way to the processing plant.

Today there are several major regions in the world with industrial scale production. World top ranking (%):

• Russia – 22;
• Australia – 20;
• Botswana – 19;
• Congo – 17;
• Canada – 10.