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Diamond industry of Botswana, its current state and prospects

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Botswana has a rich source of rough diamonds. The country’s diamond reserves reach about 340 million carats, while its resources (including reserves) exceed 905 million carats. The country is consistently among the world’s three largest diamond producers by volume and value. In 2017, Botswana produced almost 23 million carats of diamonds (the third-largest result after Russia and Canada) to the amount of $ 3.329 billion (ranking second to Russia). Virtually all diamonds in the country are mined by Debswana, which is owned in equal parts by the Botswana government and De Beers, part of the Anglo American Group.

Botswana’s raw material base is made up of huge-scale kimberlite pipes Orapa and Jwaneng. There are also several smaller deposits: Damtshaa, Letlhakane, Ghaghoo, Karowe, Lerala, BK 11 and Kx36.

The Jwaneng diamond pipe, discovered in 1972, is located in the south of Botswana and is one of the largest diamond deposits in the world in terms of diamond reserves and the world’s largest in terms of diamond value. According to the data taken at the beginning of 2018, this diamond field’s probable reserves for open-pit mining, taking into account the Cut-8 and Cut-9 expansion projects, amounted to 174.8 million carats of diamonds with an average grade of 1.265 carats per ton, while its indicated resources, excluding the reserves, reached 62.3 million carats. Another 60 million carats of diamonds were estimated and attributed to the inferred category; these resources are not included in the mining plan. In addition, the tailings of this deposit contain 72.7 million carats of inferred diamond resources.

Debswana started the Cut-8 expansion project in 2010 with an aim to deepen the quarry to 650 m and gain access to ore containing 92 million carats of diamonds; the company commenced diamond mining and processing operations in the middle of 2017. In the near future, it plans to start the Cut-9 project, which, if realized, will make it possible to additionally produce 48 million carats of diamonds.

In 2017, Jwaneng produced 11.9 million carats of diamonds. The diamonds mined at Jwaneng annually account for about 60-70% of revenues gained by Debswana.

The Orapa diamond field, giant by its mineral reserves, is located in the central part of the country within the kimberlite field of the same name. The field, which was a take-off point for the first diamond mining enterprise in Botswana, was discovered in 1967. Despite the long period of operation, the field has a significant mineral wealth of diamonds: its probable reserves for open-pit mining amount to 140.8 million carats, while its indicated resources, excluding the reserves, reach 297 million carats and inferred resources (not included in the mining plan) are estimated at 66.2 million carats. The average diamond grade in ores is lower than at Jwaneng - 0.975 ct / t. In addition, there are 130.3 million carats of indicated diamond resources in the tailings. Debswana extracted 10.2 million carats of diamonds from Orapa in 2017.

There are several other diamond deposits within the Orapa kimberlite field: Letlhakane, Damtshaa, Karowe and BK 11.

The Letlhakane diamond field is based on the eponymous low-diamond-bearing (0.2-0.3 ct / t) kimberlite pipe. The open-pit mining of this deposit by Debswana was completed in 2017 due to the exhaustion of reserves. The indicated and inferred resources of diamonds for underground mining make up only 12.3 million carats; however, there mine’s tailings contain twice as much diamonds: 8.4 million carats of probable reserves, 1.4 million carats of indicated resources and 14.1 million carats of inferred resources.

The construction of a modular processing plant to handle the dumps began in 2015, and the first diamonds were produced there in the summer of 2018. The project to recycle the tailings will extend the life of the Letlhakane mine by 25 years. Last year, the mine produced 607,000 carats of diamonds.

The Damtshaa deposit consists of five small kimberlite pipes with a low average diamond grade (0.192 ct/t), the total probable reserves of which are estimated at 4.9 million carats, their indicated resources - at 0.9 million carats and their inferred resources - at 5 million carats.

At the end of 2015, operations at the Damtshaa mine, also owned by Debswana, were temporarily suspended due to a weak diamond market situation but resumed at the end of 2017. In 2017, the mine produced 35,000 carats of diamonds.

The Karowe diamond field is represented by the AK-6 kimberlite pipe, which was discovered in 1969 and was initially recognized as unsuitable for commercial mining. However, after the exploration in the early 2000s, its parameters were significantly adjusted. As of December 25, 2017, the indicated resources of the diamond deposit were estimated at 5.59 million carats, including its probable reserves of 3.26 million carats; the mine’s inferred resources stood at 2.98 million carats. The ore quality at Karowe is low, its average diamond grade reaching only 0.14 ct/t, but this is offset by the high quality of mined stones, the cost of which varies on average from $625 to $680 per carat.

Since 2012, the deposit has been developed by Boteti Mining (Pty) Ltd, a subsidiary of Canada-based Lucara Diamond Corporation, which is currently the only diamond mining company in Botswana that is not dependent on De Beers. Last year, the mine produced 249,800 carats of diamonds. Boteti Mining plans to develop this field by the open-pit method until 2026, and then switch to underground mining.

In 2014, the company also received licenses for two promising areas near its existing asset, within which drilling is currently underway.

Five kilometers from Karowe, there is another kimberlite pipe, BK 11, containing a mineral resource of diamonds reaching only 1.2 million carats. Its ore has a low average diamond grade (0.44 ct/t). The quality of diamonds mined at BK 11 is also relatively low, their average cost is $137-157 per carat.

The owner of the field, Firestone Diamonds, which is based in Britain, commissioned the facility in August 2010 and mined about 2,000 carats of diamonds, but in February 2012 the mine was shut down due to problems with the extraction of diamonds at the concentration plant. Firestone is currently focused on its other African asset, the Liqhobong mine in Lesotho.

In the central part of Botswana, within the Central Kalahari Game Reserve, there is the Ghaghoo diamond deposit, previously known as Gope, represented by two kimberlite pipes: GO25 and GO136, the first of which is the most studied. The deposit was blocked by Kalahari sands, the overburden of which was 80 m thick. According to a recent estimate of reserves and resources conducted in 2013, the indicated resources of this diamond deposit reach 15.5 million carats, including 2.1 million carats of probable reserves, while its inferred resources are 5 million carats. Ghaghoo’s ore is characterized by a low diamond grade varying from 0.28 to 0.18 ct/t, the average diamond cost reaching $239-267 per carat.

Initially, the field was planned to be developed by the open-pit method, but this project was considered not effective. Gem Diamonds Limited based in Britain, which owns the right to develop the field, drew up a project for its underground mining with an inclined raise to access the ore and use the methods of block and sub-level caving, which allowed it to continue its development - the mine was put into operation at the end of 2014. In just over two years, the mine yielded about 143,000 carats of diamonds. However, it did not reach its full production capacity of 600,000 carats a year, as it was mothballed in February 2017 due to unfavorable conditions in the global diamond market.

Gem Diamonds, like Firestone Diamonds, is focused on developing its Letseng mine in Lesotho, known as the source of large, very high-quality diamonds.

Also, in the central part of the country, but closer to the border with South Africa, there is the Lerala diamond field, which includes five closely spaced small and low-diamondiferous (0.25-0.3 ct/t) kimberlite pipes, totaling 3.1 million carats in indicated resources together with 2.5 million carats of probable reserves (as of 2014). A mine with a concentration plant was commissioned there in 2008, its annual output capacity set at 330,000 carats of diamonds, but it was closed in 2009 due to the global downturn. After that, the mine changed several owners, until it was purchased by Australia-based Kimberly Diamonds Limited in 2014. Mining operations at Lerala were resumed in 2015, but it turned out to be a money losing business and it was again closed in May 2017. At the end of May 2018, mass media reported that the Lerala mine was sold at an online auction for $8.1 million.

Geological exploration is underway in Botswana to identify kimberlite bodies with commercial diamond content.

Petra Diamonds Limited is conducting geological exploration in the Central Kalahari Game Reserve, studying kimberlite pipe KH 36. As of June 30, 2017, the pipe had indicated diamond resources estimated at 6.32 million carats and inferred resources estimated at 2.41 million carats. The KH 36 pipe’s average diamond grade is 0.35 ct/t.

Canada-based Tsodilo Resources Ltd explores the BK 16 kimberlite pipe within the Orapa kimberlite field. In April this year, the company said it had received the first diamonds from samples, and in July it published the results of an independent estimate of the stones value, which averaged $197.68 per carat. To enrich the diamond-containing concentrate, the company used the POLUS-M separator developed by the Burevestnik Research and Production Enterprise (part of the ALROSA Group).

Botswana Diamonds PLC conducts early stage exploration in order to detect primary diamond deposits in the Gope (Kalahari Desert) and Orapa areas, including in team with ALROSA.

Pangolin Diamonds Corp. is searching for kimberlite deposits within the Malatswae project, which is located approximately 40 km from the Orapa kimberlite field. In addition, the company acquired a stake in the AK 10 project in July 2018 buying it from Makanwu Civil Blasting (PTY) Ltd. The AK 10 kimberlite pipe was discovered by De Beers in 1968 within the Orapa kimberlite field. No exploration was carried out at the field.

Thus, at present, the Jwaneng and Orapa kimberlite pipes discovered in the late 1960s and early 1970s appear to be the main source of diamonds in Botswana. If their resources are exhausted, the country’s diamond mining industry will begin to experience serious difficulties, since there are no deposits in Botswana on which large mining businesses could operate. Certain prospects may be associated with the development of deposits having small reserves with low diamond grades, but yielding high quality stones, such as Karowe, but currently it is the only one in the country. To preserve the position of one of the world’s largest diamond producers, the government of Botswana should take measures to stimulate the exploration for diamonds.

Anastasia Smolnikova, Chief Specialist, Solid Minerals Section at All-Russia Research Institute of Mineral Raw Materials