Boteti Mining is developing the high-quality Karowe diamond mine, a Type IIA mine, located in the Central District of Botswana.

Boteti proposes to develop an underground mine with a pre-production capital cost of $514m, in addition to the existing open-pit mine.

Feasibility study of the Karowe open-pit mine was completed in 2010, while a feasibility study for the underground mining operation was completed in November 2019.

Fully commissioned in 2012, the open-pit mine is expected to be operational until 2026. The underground mine will extend the mine life to 2040. The combined open-pit and underground operations are expected to yield a life-of-mine production of 7.8 million carats.

Construction of the underground mine is anticipated to be started in mid-2020, with first ore to be forwarded to the mill feed in 2023. The processing plant is expected to be ramped up to its full capacity of 2.7Mtpa by 2026.

The mine has recovered a 1,758 carats (ct) diamond, named Sewelô in April 2019. It is the biggest diamond ever recovered in Botswana. Karowe is also home to the second biggest diamond, the 1,109ct Lesedi La Rona.

Karowe diamond mine location and geology

Karowe diamond mine is located in north-central Botswana and is identified within the Orapa/Letlhakane Kimberlite district.

Discovered in 1969, the Karowe mine site is situated at an elevation of 1,020m above sea level in the Kalahari Desert. The location is accessible by the Letlhakane to Orapa road with Letlhakane village being the closest settlement.

The Karowe mine is a kimberlite body comprising three geologically distinct, integrated pipes called the North Lobe, Centre Lobe, and South Lobe. Each of the lobes contains kimberlite of a different nature with difference in the texture, weathering, and proportion of rock dilution.

Karowe diamond mine reserves

The Karowe mine contains total mineral reserves of 57.3 million tonnes (Mt) of ore containing 13.9 million carats (Mct), as of September 2019.

The total indicated resources are estimated to be 54.27Mt containing 8.3Mct of diamonds excluding stockpiles.

Mining at Karowe diamond mine

The Karowe open-pit mine, formerly known as the AK6 project, employs conventional open-pit mining method featuring drilling and blasting.

The proposed underground mine will be developed to recover ore from the South lobe kimberlite resource, which is situated below the open-pit.

Long hole shrinkage (LHS) method is proposed to be employed to access the underground mine, on a vertical retreat basis.

The mine will be accessed by using two vertical shafts of depth 765m and 715m, which will be used for production as well as for ventilation.

The underground ore will be processed at the existing Karowe processing plant. Processing of the open-pit ore is expected to terminate in 2025.

Karowe currently uses bulk sorting machines, operating on Tomra X-ray Transmission (XRT) sensors, to differentiate the liberated diamonds from kimberlite and waste host rock gangue.

Infrastructure for the Karowe underground mine

The Karowe underground mine will use the existing open-pit infrastructure, which includes administrative offices, mine vehicle workshops, a metallurgical plant, slimes dam, and stockpile and waste dump areas.

The site receives electricity from the Orapa substation, owned by Botswana Power Corporation. A new 29km-long, 132kV power transmission line will be installed to connect the mine with the Botswana Power Corporation substation.

New buildings and surface facilities are proposed to be installed adjacent to the shafts for the underground mine. Other major supporting infrastructure projects proposed include a construction camp and the expansion of coarse and fine tailings facilities.

Water required for the project is collected from an aquifer near the Ntane Sandstone Formation and the overlying Karoo basalt.

Contractors involved

Lucara engaged JDS Energy & Mining and various independent industry consultants for preparing the Karowe underground mine feasibility study.

Mineral Services Canada prepared the updated mineral resource estimate for the diamond mine.

Trollope Mining Services conducted ore mining at Karowe open-pit until 2016, while Moolmans was awarded a six-year mining contract in 2017.

DRA Global provided engineering, procurement, and construction management (EPCM) services for the design and construction of the diamond milling, dense media separation (DMS), and recovery plant at Karowe.