Free State has potential to host further commercial kimberlites – Botswana Diamonds

25th September 2018 By: Simone Liedtke - Writer

The Free State has the potential to host further commercial kimberlites, says Botswana Diamonds, referencing research in various archives into the history of diamond mining in South Africa.

Following the initial document research work and ground truthing, Aim-listed Botswana Diamonds has since started taking ground samples for whole rock geochemistry tests conducted by the Council for Geosciences.

The results of these tests and observations confirm the existence of eight kimberlites which exhibit Group 1 kimberlite geochemistry similar to the larger producing mines of Kimberley and Koffiefontein in the region. 

The existence of extensive historical working supports the nature of these kimberlites as being diamondiferous. 
 
Detailed ground geophysics followed and produced minimum sizes for the two clusters of eight kimberlite pipes of between 0.3 ha and 1.15 ha, which the company noted excludes extensive kimberlite dyke development along some of the properties.

These sizes were determined using a combination of magnetic, electromagnetic and gravity geophysical techniques, which has resulted in strong images of the footprints of these kimberlites.
 
Mineral chemistry work was then undertaken to rank the kimberlites from the perspective of diamond-bearing potential.

The analyses of 3 100 garnets and spinels at the University of Johannesburg indicate high abundances of diamond inclusion type chemical compositions, thereby rating these kimberlites as being of high interest in terms of diamond-bearing potential.

The results also indicate a preponderance of G9 and a few G10 garnets, which Botswana Diamonds pointed out is similar to the chemical signatures present in the neighbouring iconic mines at Jagersfontein and Koffiefontein.
 
The mineral chemistry result supports the conclusions from the previous whole rock geochemistry and from the geophysics in addition to field observations.

The research also identified that in addition to the well-documented iconic operations at Jagersfontein, Koffiefontein and Kimberley, a number of smaller diamond mines existed to the east of Bloemfontein and extended west to Kimberley.

Forming part of Botswana Diamonds’ Free State project in South Africa, the research, which was undertaken during a field trip this month, also found that, in addition to the law at the time not requiring formal documentation regarding any diamonds discovered, there was extensive document loss and destruction consequent to the Anglo Boer war from 1899 to 1902.

Despite this, the company on Tuesday noted that “much is still available” and that there remains considerable anecdotal evidence from the time.

Owing to aerial imagery and ground truthing having partially completed the jigsaw, Botswana Diamonds will focus its attention on areas within its Koppiesfontein, Poortjie, Swartrandsdam and Tafelbergsdam properties, which the company said were “historic workings and abandoned equipment are clearly evident”.

These results, directors at Botswana Diamonds believe, justify moving to a phased drilling programme, the timing of which will be announced in due course.

According to Botswana Diamonds chairperson John Teeling, the next step is “drilling to determine the kimberlites’ current commerciality”.