Results from survey work conducted at Botswana Diamond's Free State project, located between Bloemfontein and Kimberley, had indicated that sizes of kimberlites there ranged from 0.3 hectares to 1.15 hectares, the board of Botswana Diamonds announced on Friday. Following their announcement regarding the re-discovery of eight Group 1 kimberlites, Geofocus undertook detailed ground geophysical survey work aimed at determining the surface area of these kimberlites. Results indicate the sizes of these kimberlites to range from 0.3 hectares to 1.15 hectares (click through for details). The next phase of work at the Free State project will consist of an analysis of the indicator mineral chemistry for each of the pipes to determine an economic interest rating which will prioritize further work. This follows field observations of extensive historical workings which suggest that these kimberlites are diamondiferous. This is planned for early in 2018.
The kimberlites occur along a kimberlite feeder system where the diamond mines of Jagersfontein, Koffiefontein and Kimberley are located. It is therefore inferred that the eight kimberlites were formed at the same time as these mines. Recent whole rock geochemistry shows similar compositions in the kimberlites to the surrounding mines. Jagersfontein is renowned for the blue gems it produced, and the Excelsior (972 carats) and Reitz/Jubilee (651 carats) diamonds recovered from it are amongst the 10 largest diamonds ever discovered, while Koffiefontein is renowned for the high-quality gems it produces. John Teeling, Chairman, commented, "The re-discovery of 8 kimberlites in a highly prospective diamond area was very positive. We now know the sizes of each pipe/dyke and we believe that each could contain diamonds. The next step is to evaluate the diamond indicator minerals in each pipe to decide priorities for drilling."