Mineral ResourceMining

Diamond Mining – How Diamonds Are Mined And Processed

Story Highlights

  • How Diamonds Are Mined And Processed
  • THE PROCESS OF ORE TO EXTRACT ROUGH DIAMONDS
  • Diamond Mining & Diamond Mines Across The World

The diamond industry goes through a succession of proceedings before it reaches the wearer or final consumer. Diamond mining is the first procedure in the production of diamonds, but before diamonds are mined, careful analysis of the scalability & profitability of the mine is done.

Diamond mining is the activity through which diamonds are retrieved from deposits such as gravel, sand & clay. Diamond mining is a time-consuming and capital intensive industry which is marked by high investment,
strict regulations, government investment and is conducted by mining companies.

Currently, there are a limited number of diamond mines operating across the world, 50 of the biggest mines account for 90% global supply chain.

How Diamonds Are Mined And Processed

Diamond Mining - How Diamonds Are Mined And Processed

There are three main types of diamond mining:

  •      Pipe mining (primary deposits) consisting of open-pit mining and underground mining;
  •      Alluvial mining (secondary deposits);
  •      Marine mining

Diamond Pipe Mining

There are two types of pipe mining: open-pit mining and underground mining.

Before any actual mining even takes place, prospectors need to locate the diamond sources first. Geologists do this by following the trail of secondary diamond sources (e.g. river beds) to determine where the primary sources of pipe deposits are.

Once the pipes are found, ore samples are examined to evaluate suitability and profitability in mining. If the presence of diamonds is proven true and profitable, shanks are inserted into the ground at the ore-bearing pipes and huge amounts of soil are extracted.

To make mining efficient and effective, the raw rock and soil are typically not examined on-site. Instead, they are transported to special plants where the ore is processed and the rough diamonds are extracted. Depending on how rich the ore is, a few hundred tons of ore might be sieved just to produce a single carat of gem-quality rough diamonds.

Even after extraction, the rough diamond is still far from being set in an engagement ring. In heavily secured facilities, rough stones are sorted into various gem-quality categories and industrial-specific grades. Thereafter, the roughs are sold, cut, polished and commercialized.

As you can imagine, the journey a rough diamond undergoes from its violent formation process to being mounted on an exquisite setting is a long process and passes through many different channels.

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Alluvial Diamond Mining

 

Another mining method that is frequently used is called alluvial mining. This type of mining is usually performed in areas of secondary deposits like riverbanks, beaches or even off-shore locations.

Alluvial mining involves the building of walls and the diversion of rivers. Once the water is emptied out and prevented from flowing into the area of interest, bulldozers are then used to exploit the ground of the riverbank.

Usually, kimberlite ore can be found in depths of at least 15 meters. When the diamond-rich depth is reached, the raw material extracted from the ground is then transported to a special screening plant for further processing.

There’s another form of alluvial mining called artisanal mining. In essence, it is basically the same method employed by gold diggers which involves the screening and straining of mud.

In the case of artisanal mining, the extraction process usually takes a longer time as it involves low tech equipment and manual labor. Compared to alluvial mining, the post-processing is shorter and is a less resource-consuming task as diamonds are identified in situ of the work area.

Offshore Marine Diamond Mining

 

Deposits of diamonds found in marine bodies are a result of kimberlite pipe erosion. When heavy rain occurs, the exposed diamonds are washed into rivers and carried towards the coast.

Namibia is a country that holds the biggest quantity of gem-quality marine deposits in the world. Currently, the country has a partnership with De Beers to conduct marine-based recovery and it has produced more volume than land-based mining.

Because marine deposits are distributed over large areas unevenly, mining companies utilize different methods to mine them. Some of these methods include shallow-water mining, deep-sea operations involving high tech equipment and simple alluvial mining.

Like open-pit mining, the ore materials are usually transported offsite for further processing.

Extracting Diamonds

There are 5 different stages in which diamonds are recovered from ore:

STAGE 1: CRUSHING

Diamond-bearing ore and gravel is collected and transferred to a primary crusher, which is responsible for reducing the larger pieces of ore into smaller pieces that measure no larger than 150mm, and are much more manageable. A secondary crusher (also called a roll-crusher), is sometimes used to break the ore down into even smaller pieces.

STAGE 2: SCRUBBING

In the scrubbing stage, the pieces of ore are scrubbed in order to remove any loose excess material attached to them, and are then screened. Pieces of ore smaller than 1.5mm are discarded, as it is too costly to extract diamonds from such small pieces.

STAGE 3: CYCLONIC SEPARATION PLANT

A solution comprising ferrosilicon powder and water is mixed to a specific density, and mixed with the diamond-bearing ore. Once mixed, the solution is inserted into a cyclone, where it is tumbled and, in this process, forced to separate. The materials with the highest density sink to the bottom of the cyclone, and as a result, a layer rich in diamond concentrate is formed.

STAGE 4: RECOVERY

The diamond-rich concentrate goes through various processes that involve magnetic susceptibility, x-ray luminescence and crystallographic laser fluorescence. These processes are calculated based on the unique properties of diamonds. These processes separate the rough diamonds from the other heavy density materials that were collected in the cyclone separation plant. Diamonds emit flashes of light which are detected by sensors. This sends a signal to a microprocessor, which in turn fires a blast of air in the direction of the diamond. The diamond is then split into a collection box.

STAGE 5: CLEANED, WEIGHED AND PACKAGED

The diamonds collected in the collection box are then cleaned in an acid solution before being washed, weighed and packaged for transportation. Each container is thoroughly sealed as per the Kimberley process – they have a tamper-resistant seal and are numbered on site.

Diamond Mining & Diamond Mines Across The World

The largest diamond producers are South Africa, Angola, Botswana, Namibia,  Democratic Republic of Congo (DRC),  Russia and Canada while other industry producers like Australia, Ghana, Guinea, Guyana, Lesotho, Sierra Leone, and Zimbabwe produce less than one million carats per year.

South Africa remains the leading diamond producer in the world. with South Africa widely regarded for its top quality diamond deposits.

Diamond Mining In Jwaneng & Orapa Diamond Mines Botswana

 

Botswana is one of the top diamond producers in the world measured by value and secondly, by volume. There are two major diamond mines in Botswana, they are Jwaneng diamond mine & the Orapa diamond mine.

The Jwaneng diamond mine is the richest diamond mine in the world. Jwaneng, meaning “a place of small stones”, is owned by Debswana, a partnership between the De Beers company and the government of Botswana. It was discovered in 1972 and reached full production in July 1982. The mine was officially inaugurated in August 1982.

Jwaneng is an open-pit mine. The mine produces 9.3 million tons per year of ore and an additional 37 million tons per year of waste rock. The mine is located on three kimberlite pipes that converge near the surface, covering 520,000 square metres at ground level. Currently, the mine produces approximately 11 million carats (2,200 kg) of diamonds.

Orapa diamond mine is the ninth biggest diamond mine in the world. The Orapa diamond mine stands second among the world’s biggest diamond-generating kimberlite mines. It is made up of two separate pipes, which are believed to have formed approximately 93 million years ago.

It produces approximately 20Mtpa of ore and 40 million tonnes of waste per year.

Production of the diamond at the Orapa mine commenced in July 1971. The mine treated 12.25 million tonnes of ore and produced approximately 11.08 million carats of diamonds in 2012. A record of 17.3 million carats of diamonds were produced in 2006.

Debswana, a joint venture of De Beers and Botswana Government owns the diamond mine. The mining operations are expected to continue until 2033.

The Southern African country is known for having seven well-established mines with Orapa and Jwaneng being the two most established diamond mines in the world. Both of these mines are operated by the De Beers Diamond Company. Even Meghan Markle’s engagement ring consists of diamonds from the country and till today, De Beers diamond sources a majority of their diamonds from Botswana.

Diamonds from Botswana all come in different sizes, colour, and clarity with a high volume of gem-quality stones. These exquisite diamonds are dodecahedral shaped and all come in medium to high colours covered with greenish skin.

Diamond Mining In South Africa

South Africa is home to the most breathtakingly beautiful diamonds in the world. Diamonds of all shapes and sizes have been discovered in the remarkable diamond country. One of the largest gem-quality diamonds, The Cullinan was discovered in South Africa; the exquisite diamond weighed an estimated 3106 carats.

While diamond mining has been taking in place in South Africa for almost a century and a half, the country’s diamond sector is far from reaching the end of its life. Developments at the country’s three largest mines are designed to expand their outputs and to extend their lives to anywhere between a quarter and a half a century.

The underground mining and recovery of diamonds continue to this day in the vicinity of Kimberley, the site of the early main discoveries in the 19th century. It is, however, on a limited scale with a major focus on reprocessing old tailings dumps to recover diamonds left behind by older recovery processes.

To the west of Kimberley, and on the southern banks of the Orange River some 60km upstream from Port Nolloth, Trans Hex mines largely alluvial diamonds at its Baken and Bloeddrif operations.

Further north in Limpopo province, the Venetia mine owned by De Beers is South Africa’s largest diamond producer, recovering some 8Mct a year. Mining is currently by opencast methods but the depth limits of the open pit are being reached and an underground mine is being developed to continue production below the open pit. Underground mining will be by conventional block-caving or sub-level caving methods.

The Finsch mine, part of the Petra Diamonds group, is South Africa’s second-largest producer and operates exclusively as an underground mine using conventional sub-level caving methods. Finsch produced 1.8Mct in 2019.

Near Pretoria and also part of the Petra group, plant optimisation at the Cullinan mine is ongoing – its production was 1.7Mct in 2019. Cullinan contains a world-class gross resource of 154.9Mct as at 30 June 2019, which suggests its mine life could be significantly longer than the current mine plan to 2030.

Diamond Mining In Marange & Murowa diamond mines Zimbabwe

A great portion of the land in Zimbabwe has been mined for diamonds, leading to a few well-established mines in the area. For example, Murowa mine, operated by Rio Tinto is known for regularly producing breathtakingly beautiful shaped medium-range colour diamonds with a high quality. Other larger sized diamonds are discovered through alluvial mining; the diamonds found through this method are usually coated in a variety of skin colours resulting in fancy colour stones. These alluvial mines are operated in Marange by local as well as international companies.
 The Marange Diamond Mine is the largest diamond producing project in the world, estimated to have produced 16.9 million carats in 2013, or 13% of global rough diamond supply. Marange is estimated to have produced 12.0 million carats in 2012, 8.7 million carats in 2011, and 8.2 million carats in 2010. While some diamond mines produce rough valued at over $1000 per carat, average production at Marange is estimated at under $50 per carat.
The Murowa Diamond mine is majority-owned and operated by the Rio Tinto Group, which also owns the Argyle diamond mine in Australia and part of the Diavik Diamond Mine in Canada. The mine is a combination of open pit and underground construction; current estimates put construction costs at $61 million USD and mine reserves are 19 million tonnes of ore, with an ore grade of 0.9 carats (180 mg) per tonne.

Diamond Mining In Angola

Angola is known for having an extensive resource of diamond deposits, especially in the Lunda Norte and Lunda Sul province.  One of the most well-established mines in the country is the Catoca diamond mine.

The Catoca diamond mine is the fourth largest diamond mine in the world. The mine is owned by a consortium of international mining interests, including Endiama (the state mining company of Angola) (32.8% ownership), Alrosa of Russia (32.8%), Odebrecht of Brazil (16.4%), and the Diamond Finance CY BV Group (16.8%). The mine is located on a kimberlite pipe.

The open-pit mine has an expected mining life of 30 years and is operated by Sociedade Mineira de Catoca. The mine has a reputation for producing an estimated 7 million carats each year.

The rough diamonds typically found in Angola are round dodecahedral diamonds of medium and yellowish colour with a more than usual production of larger diamonds. Most of the diamonds are sourced through an agreement by the state-owned mining company, ENDIAMA.

Diamond Mining In Lesotho

Even though Lesotho doesn’t have a large number of diamonds they produce on regular bases, the country maintains its reputation with its consistent production of very large diamonds. Some of the diamonds mined on yearly bases are larger than 100 carats. The mine primarily responsible for the production of larger diamonds is Letseng, the world’s highest diamond mine. Other developing diamond mines include Lemphane, Liqhobong, the Mothae project and the Kao mine.

Diamond Mining In the Democratic Republic Of Congo

The Democratic Republic of the Congo had the world’s second-largest diamond reserves as of January 2015, at 150Mct, or 20.5% of the global total. Substantial diamond reserves are located in Kasai Occidental and Kasai Oriental, most being alluvial and kimberlitic deposit types.

Diamond Mining - How Diamonds Are Mined And Processed

Most of the diamonds are discovered through alluvial mining by artisanal miners, as there are no official diamond producers in DRC. De Beers has a 20% stakeholder in Belgian company Sibeka, who produces one-third of the diamonds in the country. Up until this day, only a small part of the country has been mined for diamonds using modern technology; the DRC has a lot of potential for mining sectors in certain parts of the country that yet still need to be explored.

Diamond Mining In Canada

Did you know the first ever Canadian mine opened in 1998, over a century after diamonds were discovered in South Africa? In 1991 two men named Chuck Fipke and Stewart Blossom discovered a kimberlite pipe filled with diamonds close to Yellowknife, in the Northwest Territories. This resulted in Canada becoming one of the leading diamond producers in the world. Today, the country has four working mines located in Diavik, Ekati, Snap Lake and Victor.

Canadian diamonds are generally white or brown in colour. Each Canadian diamond is accompanied with a certificate of Authenticity; the certificate includes the official polar bear insignia from the Government of the North West Territories.

During the year 2017, Canadian mines produced 23 million carats of diamonds, valued at $2.6 billion. Russia, Botswana, Canada, Congo, D.R., and Australia produce over 80% of the world’s diamonds. As of 2002, Canada is currently the seventh most important diamond producer by weight and fifth by value.

Diamond Mining In Russia

Russia is one of the largest diamond producers in the world. The diamonds most commonly found in the country is known for their eight facets and sharp corners. The diamond mines in Russia, however, have a good reputation for producing diamonds of all shapes, colours and clarities. The country is home to five open-pit mines, fourteen alluvial placers and four underground mines located in Yakutia; all of which are operated by ALROSA. Another well-established mine is the Grib diamond mine operated by LUKoil.

 

Diamond Mining In Australia

Australian Mining organisations have been established since 1908 and still continue to play a significant part in the diamond industry. The country is one of the leading colour diamond producers in the world. The colour diamonds that are predominantly found in Australia is pink, purple and red.  It additionally provides a large proportion of other naturally coloured diamonds, including champagne, cognac and rare blue diamonds.

Most of these extraordinary diamonds are discovered at the largest diamond mine in Australia, Argyle. The well-known mine is operated by Rio Tinto and produces up to 12 million carats each year.  Argyle used to be an open mine pit mine, but over the years it has become an underground operation.

Other mines that play an important role in Australia and in the mining industry as a whole, is the Ellendale and Merlin mine. Today, diamond mining is considered one of Australia’s most powerful industries.

 

 

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