Operations / Botswana

Karowe Mine

Location Botswana
Ownership 100% - Boteti Mining (Pty) Ltd.
Royalty 10%
Type Hard rock. Open pit. �Mine plan to depth of 324 m.
Status Full production
Resources and Reserves Mine plan based on Probable reserves to a depth of 324 m of 33.1 mt containing 5.1 million carats

Remaining Indicated resource from surface to a depth of 400 m of 48.07 mt containing 7.61 million carats

Inferred resource from 400 m to 750 m of 21 mt containing 3.04 million carats

(Karowe Diamond Mine Botswana NI 43-101 Independent Technical Report Revised, Effective date December 31, 2013, Report date February 4, 2014)
Mine Life 13 years
Throughput 2.2 - 2.3 Mt in 2015
Capital Expenditure 2015 $62.5 - $63.5 million
Operating Costs $33 - $36 per tonne approx.
Contract Mining, Contract Process Plant Operations and Maintenance
Production 350,000 to 400,000 carats in 2015
Diamonds Significant population of Type IIa stones
  Cautionary and Forward Looking Information

The Karowe Mine is based on the AK6 kimberlite pipe, which is part of the Orapa Kimberlite Field ("OKF") in Botswana. The bedrock of the region is covered by a thin veneer of wind-blown Kalahari sand and exposure is very poor. Rocks close to surface are often extensively calcretised and silcretised due to prolonged exposure on a late Tertiary erosion surface (the African Surface) which approximates to the present day land surface.

The OKF lies on the northern edge of the Central Kalahari Karoo Basin along which the Karoo succession dips very gently to the SSW and off-laps against the Precambrian rocks which occur at shallow depth within the Makgadikgadi Depression.

The OKF includes at least 83 kimberlite bodies, varying in size from insignificant dykes to the 110 ha AK1 kimberlite which is Debswana's Orapa Mine. All kimberlite intrusions are of post-Karoo age. Of the 83 known kimberlite bodies, five (AK1, BK9, DK1, DK2 and AK6 which is the Karowe Mine) have been or are currently being mined, and a further four (BK1, BK11, BK12 and BK15) are recognized as potentially economic deposits.

The country rock at the Karowe Mine is sub-outcropping flood basalt of the Stormberg Lava Group (approximately 130 m thick on the Karowe property) which is underlain by a condensed sequence of Upper Carboniferous to Triassic sedimentary rocks of the Karoo Supergroup(approximately 245 m thick on the Karowe property). The Karoo sequence overlies granitic basement.

AK6 is a roughly north-south elongate kimberlite body with a near surface expression of ~3.3 ha and a maximum area of approximately 7 ha at ~120 m below surface. The body comprises three geologically distinct, coalescing pipes that taper with depth. These pipes are referred to as the North Lobe, Centre Lobe, and South Lobe.

The AK6 kimberlite is an opaque-mineral-rich monticellite kimberlite, texturally classified primarily as fragmental volcaniclastic kimberlite with lesser macrocrystic hypabyssal facies kimberlite of the Group 1 variety. The nature of the kimberlite differs between each lobe, with distinctions apparent in the textural characteristics, relative proportion of internal country-rock dilution, and degree or extent of weathering. The South Lobe is considered to be distinctly different from the North and Centre Lobes which are similar to each other in terms of their geological characteristics. The North and Centre Lobes exhibit internal textural complexity (reflected in apparent variations in degree of fragmentation and proportions of country-rock xenoliths) whereas the bulk of the South Lobe is more massive and internally homogeneous.

The upper parts of all three lobes contain severely calcretised and silcretised rock. This zone is typically approximately 10 m in thickness, but can be up to 20 m in places. Beneath the calcrete and silcrete, the kimberlite is highly weathered. The intensity of weathering decreases with depth with fresh kimberlite generally intersected at about 70 m to 90 m below present day surface. A unit within the South Lobe (a variety of M/PK(S)) has been found to be hard, and to produce a very large DMS concentrate primarily as a consequence of an abundance of fresh olivine in the kimberlite.