Modern Mining July 2018

COUNTRY FOCUS: BOTSWANA

an autogenous (AG) mill. The AG mill acts as a tumbling mill where the ore is reduced in size by the interaction between the pieces of ore through tumbling. This non-crushing process, along with more sophisticated sensor-based bulk sorting using X-Ray Transmission (XRT) technology supplied by the Tomra Group, has resulted in less diamond breakage and the abil- ity to recover the exceptional over-size stones for which Karowe is now famous. Between July 2012 and December 2017, over 2,0 million carats (Mct) were mined and sold, generating in excess of US$1,2 billion in revenue. Diamonds greater than 10,8 ct in weight, the lower threshold for exceptional size stones, represent approximately 5 % by weight of all diamond production over the life of mine to date. Life of mine average stone size for the +10,8-ct production is 27,8 ct/stone. Lucara sells its production in Botswana through regu- lar and exceptional stone tenders. The largest stones are sold through the exceptional stone tenders, where buyers submit sealed bids over a number of days. There are about four to five regular and one to two exceptional stone ten- ders each year. By the end of 2017, Lucara had sold 156 exceptional diamonds for more than US$1 mil- lion each, generating US$598 million. In 2015, with the commissioning of the XRT circuits, Karowe ‘rocked’ the diamond world with the recovery of seven +300-ct dia- monds. Three of these incredible exceptional stones were recovered in the same week in

concluded that A/K6 could be developed into a mine with the project delivering an NPV of US$189 million. The capital invest- ment required was estimated at just US$165 million. This study also proved the pipe actu- ally had an area of 4,2 ha at surface which expands to 7,0 ha at a depth of 120 m and also has a much higher diamond grade of 19 car- ats per hundred tons (cpht) with a price tag of US$183/ct (rough diamonds are valued based on their size, shape, quality and colour, other- wise commonly known as the 4Cs (carat, cut, clarity and colour), a grading system which was invented by the Gemological Institute of America back in 1953). In the same year, Lucara bought African Diamonds’ 30 % shareholding in the A/K6 project for US$70 million in stock, thus making Lucara the sole owner through Boteti Mining. Lucara is now valued at almost US$1,0 billion – a remarkable figure since it paid only US$120 million for Karowe seven years ago. The Karowe mine was commissioned in 2012 and consists of three lobes, South, Centre and North, of which the South Lobe makes up approximately 75 % of the kimberlite’s original resource potential. Construction of the mine required a capital investment of approximately US$120 million, which includes the process plant and all mine site and off-site infrastruc- ture. Karowe now employs over 800 people, more than 98 % of them Botswana citizens. Instead of using conventional scrubbers and crushers to disaggregate the kimberlite ore in order to liberate the diamonds, this mine uses

Above: An aerial view of the Karowe mine, which is located in the Orapa Kimberlite Field. Right: Debswana’s Jwaneng mine, seen here, is a very much larger operation than Karowe. Although it does not have the same record of producing large stones as Karowe, a 425-ct gemwas recovered at the mine in January 2016.

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42  MODERN MINING  July 2018