Kalahari Diamonds

In September 2005, Petra acquired 100% of Kalahari Diamonds Limited and subsequently became the holder of a large land area under diamond prospecting licence in Botswana, all of which is "on craton" (the geological formation known to host diamonds).

Botswana is the world’s largest producer of diamonds by value and it offers an exceptional basis for exploration in that it ranks highly with regards to diamond prospectivity, yet it generally ranks well with regards to operating costs.

Kalahari, through its wholly-owned Botswana subsidiary, Sekaka Diamonds, is the holder of approximately 22,250 km² of diamond prospecting ground. In addition to this landholding, a further 1,500 km² have been designated for allocation to Petra, with a further 6,000 km² being under application.

Petra’s prime focus is to evaluate recent discoveries with a view of further developing these potentially economic orebodies.

Kalahari Diamonds' current project landholding is largely within the Central Kalahari Region. These areas are predominantly covered by tertiary sediments of Kalahari sand cover, ranging in thickness from almost 30 metres in the South, to a maximum of 120 metres in the Eastern part of the Central Kalahari Game Reserve (CKGR). The pre-Kalahari geology is relatively consistent, wholly covered by the Stormberg flood basalts of the Karoo Supergroup. Beneath the basalt lies the sedimentary sequence of the Karoo Supergroup (Lebung, Beaufort, Ecca and Dwyka Groups).

The precise thickness of the basalt in the CKGR is unknown, but it is evident from the Government of Botswana’s aeromagnetic survey data that the basalt is heavily faulted and its thickness varies considerably from area to area, thus making the area structurally complex. Major faults seem to have a North-West – South-East and North-East – South-West orientation. These major structures are the main targets in kimberlite exploration as they are zones of structural weakness where kimberlites may be emplaced.

During FY 2011, large tracts of well-explored ground that had come to the end of their seven year licence tenure were relinquished, resulting in a total current landholding of some 22,250 km², which is one of the largest diamond exploration holdings in the country.

Geophysical ground follow-up and Heavy Mineral Analysis of 46 high priority targets selected from High Resolution Airborne Magnetic data were completed across Petra’s various project areas. At the end of FY 2011, six targets had been drilled as part of an on-going exploration drilling campaign – no additional kimberlites were discovered.

In addition, a 4,500 line kilometre Xcalibur HiRes Airborne Magnetic Gradiometer survey was successfully commissioned and conducted over historical kimberlite indicator mineral recoveries in the Kukama East project area. The application of Xcalibur Airborne Geophysics’ horizontal gradient magnetic acquisition system remains Petra’s primary exploration tool to be utilised in clearly defined areas of interest and a 22,000 line kilometre survey covering newly acquired ground is now planned.

Initial delineation drilling (five boreholes, totalling 1,730 metres) undertaken on the Kx36 kimberlite was completed by the end of FY 2011. All boreholes were surveyed (directional) and a down-hole geophysical wireline logging programme was successfully completed. Following detailed lithological logging of all drillcore retrieved, samples were submitted for petrographic and micro-diamond analyses. All results (expected FY 2012) will be used to update the existing 3D geological (Gemcom) model to assist with the calculation of material volumes and a preliminary grade estimate.

Significant progress has also been made with both the geophysical and geological 3D modelling of the portion of kimberlite BK1S discovered on Petraground adjoining the Damtshaa Mining Licence in mid-2008. Results will be used for the calculation of material volumes for the portion of the kimberlite body BK1 that falls outside the Debswana mining lease and within Petra’s prospecting license.