In the early years of its nationhood, Botswana was one of the poorest countries in the world, with a per capita income of about $80 a year. Today, it is among the most prosperous countries in Africa, with a real middle class, and a per capita income approaching $6,000 a year. By contrast, the average citizen in Angola earns about $2,500 a year, while in the Democratic Republic of the Congo, it’s a little more than $1,500, according to the World Bank.

Botswana is a success story. Because of diamonds the landlocked, arid country of 2.3 million people moved from being one of the poorest countries in Africa to one of the most successful medium-sized economies with more than 80% of diamond profits staying within the country. Much of this income benefits citizens through free education, free healthcare, an expansion of local jobs in the diamond industry, and plan for a more diversified economic future.

There is no question that the discovery of diamonds was the most important catalyst in Botswana’s economic growth. Botswana has produced more than 728 million carats of rough diamonds since operations began there in 1971 and is the source of many of the world’s largest and most beautiful diamonds – including the 1,109-carat Lesedi La Rona, which was uncovered in November 2015. The revenue raised from selling these precious stones has gone into improving the lives of Botswana’s small population. Such is their importance that diamonds contribute approximately 30 percent of the country’s GDP and account for 70 percent of all exports by value.

Companies like De Beers have played a pivotal role, working together with the government of Botswana through Debswana, to create a sustainable industry that benefits the people of Botswana through proper exploitation of this mineral resource.

In July 1988, De Beers covered the Lerala area in east Botswana with reconnaissance loam sampling. After the initial positive results from the reconnaissance program, Grid Loam Sampling (DGL) and Detailed Grid Loam Sampling (DGLS) led to the discovery of two kimberlites clusters in 1991: one comprising three pipes (K1, K7 and K8) close to the Lotsane River, and the other five pipes (K2, K3, K4, K5 and K6) near the Susulela River. It is the latter group of kimberlites that proved diamondiferous and has been subjected to several trial mining operations.

The former cluster produced very few garnets, is diamond-poor but dominated by ilmenite. The diamondiferous kimberlites are garnet-bearing and ilmenite-poor. Interestingly the samples, which eventually led to the discovery of the two groups of kimberlites, were rich in ilmenite that came from the first cluster.

TSince the discovery of the first kimberlite in Botswana in 1967, a total of 386 kimberlites have been found mainly associated with 12 kimberlite clusters (Fig. 2). Of these 16 kimberlites from four clusters have produced or are producing diamonds, and these are: Orapa (AK1, Karowe-AK6, Letlhakane-DK1 & DK2, BK11, Damtshaa-BK1, BK9, BK12 & BK15), Ghaghoo (Go-25), Jwaneng (DK2), and Lerala (K2, K3, K4, K5 and K6).

In December 2015, Kimberly Diamond Limited (KDL), announced an updated JORC2012 Resource Estimate for the Lerala Diamond mine totalling 20.11Mt at 24.22 cpht for a total of 4.8 Mcts. An additional 3.79 Mt at 26.54 cpht was also defined as an Exploration Target. These tonnes lie primarily below the current Resource outline.

Resource estimate was generated by applying a “reasonable prospects for eventual economic extraction” test to geological models of the Lerala kimberlites. The Indicated portion of the Resource extends to depths where good drilling coverage is present and both lithological and grade data are available. The Inferred portion of the Resource extends 40 m below the Indicated portion and is defined by limited lithological data and no grade information. Here, grade estimates have been projected down from the Indicated portion of the Resource.

De Beers, which had conducted trial mining at Lerala in the late 1990’s in order to obtain sufficient data to support a robust diamond valuation and a full-scale mine feasibility study, had intended for the operation to be self-funding however they failed to achieve the expected diamond recoveries as a result of unquantified diamond theft, continued plant inefficiencies and inaccurate assumptions as to the nature of the kimberlites being treated.

DiamonEx Ltd that acquired the project permit in 2002 and following further exploration and evaluation, appointed ProMet Engineering to construct and commission a 200 tph processing plant. Between June 2008 and January 2009, approximately 300,000 t of ore were processed, and 49,470 carats were officially reported to have been recovered.

Unfortunately, the designed head feed tonnages were never achieved resulting in increased operating costs and the recovery section of the plant did not perform efficiently. This, together with the diamond price crash in August 2008 due the international credit crunch, resulted in an unprofitable operation. DiamonEx had no option but to enter into judicial management in January of 2009.

Fig. 2:Lerala Diamond Mine aerial view

Mantle Diamonds undertook a major plant evaluation and modification between May 2011 and March 2012 in order to overcome the inefficiencies that plagued the initial plant design. Following the modifications, Mantle attempted to ramp up throughput to 130,000 tpm but was forced to suspend production after 5 months and before this target could be met. Furthermore, the recovered diamond grade was only a quarter of the estimated head grade, indicating significant diamond losses throughout the processing circuit.

From August 2012, Mantle set up a small facility to reprocess 410 t of recovery plant tailings and managed to recover a further 42,556 carats. When this result is combined with the ROM production data, the total recovered grade is calculated to be 28.2 cpht.

Fig. 3: Modified Processing Plant at Lerala

Botswana is the world’s largest producer of diamonds by value currently with eight operating mines. Diamond prospecting was an enormous challenge in the remoteness of the Kgalagadi Desert which makes up more than 80% of the country. In fact, it took one and a half decades after the first few rough diamonds were discovered in 1955 to open Botswana’s first diamond mine at Orapa in 1971.

The first diamondiferous Kimberlite, known as B/K1 pipe, was discovered in Botswana 15km north of Letlhakane in 1967, a year after Botswana gained independence from British colonial rule over the then Bechuanaland Protectorate. However, the first recognised diamond find in Botswana, in alluvial deposits, was made by Central African Selection Trust prospecting geologists in 1955 on the banks of the Motloutse River at Foley siding, some 250 km east of Orapa.

A very important point to make early on is just how rare and therefore valuable diamonds are. Of the approximately 6,800 kimberlites discovered globally to date (2018), less than 1000 (18%) are diamondiferous and less than 65 (1%) are economically viable to be mined, while about 7 (0.1%) are tier 1. Although more than 380 kimberlites have been found in Botswana, less than 10 are being economically mined.

Since the discovery of the first kimberlite in Botswana in 1967, a total of 386 kimberlites have been found mainly associated with 12 kimberlite clusters (Fig. 6). Of these 16 kimberlites from four clusters have produced or are producing diamonds, and these are: Orapa (AK1, Karowe-AK6, Letlhakane-DK1 & DK2, BK11, Damtshaa-BK1, BK9, BK12 & BK15), Ghaghoo (Go-25), Jwaneng (DK2), and Lerala (K2, K3, K4, K5 and K6).

Botswana is the world’s largest producer of diamonds by value and since independence diamond revenues have contributed significantly to the country’s development. In light of imminent resource depletion, in 2005 the Government signed an agreement with the country’s largest diamond producer, DeBeers, to add value to diamonds by beneficiating them locally.

Fig. 7: Women cut and polish diamonds in Botswana

June 2014, 20 cutting and polishing firms, known as Sightholders, had been licensed and were operating in Botswana. These firms receive regular rough diamond allocations on a number of conditions, including training locals with cutting and polishing skills. Traditionally the cutting and polishing skills was a craft that was learnt through long apprenticeships. However, the technological revolution that started in the industry in the 1980s has changed the nature and mix of skills used in cutting and polishing process. Technologies like laser, computer numerically controlled machines and computer-aided design have increased accuracy and improved the quality of the polished diamonds. These technologies have also simplified the skills needed by production workers and simultaneously enhanced the skills required in machine maintenance.