AK8

AK8 is one of 30 known kimberlites being explored by De Beers as part of the Boteti Exploration Joint Venture between African Diamonds and De Beers. Pipe AK8 is now estimated from ground geophysics at around 6 hectares in size. Fifty-four stones weighing a total of 6.33 carats including one 2.26-carat stone, were recovered from the 98 tonnes extracted from four holes in the kimberlite using 12-inch drilling. Two of the four holes were negative and two were positive for macrodiamonds. The negative holes drilled into significant intersections of basalt and basalt breccia, despite the fact that their adjacent pilot holes intersected kimberlite. Of the three positive holes, one sampled 154m of kimberlite, of which 80m was highly diluted (80%) by basalt breccia. One hole which sampled some 151m of consistent kimberlite yielded 4.395 carats from 26.44 tonnes of.sample.

Bulk sample results were obtained from four 12" diameter drill holes; the data are summarised in the Table below:

Drillhole Depth Sample Tons Carats Stones
LDD_001 30 - 164m DCD 172 25.421 1.54 23
LDD_002 20 - 89m DCD 176 13.090 0 0
LDD_002 89 - 124m DCD 173 11.383 0 0
LDD_003 77 - 200m DCD 174 21.540 0.39 7
LDD_004 14 - 165m DCD 175 26.443 4.395 24

The AK8 recovery comprises 54 stones weighing 6.33 carats. There are some interesting features of the data:

  • Two samples had nil recoveries
  • About half the caratage recovered from sample DCD 175 is from one stone (2.26cts)
  • Generally the sample results vary significantly, the raw sample grade estimates range from 0 to 16cpht.

Three grade scenarios were examined, the total recovery, positive recovery (excluding samples DCD 173 and 176) and sample DCD 175.

Scenario AK8 (grade - cpht)
  Raw Modelled
Total recovery 6.4 5
Samples 172, 174 & 7.8 7
Sample 175 16.4 30

The grade estimates vary considerably, particularly when only considering sample 175.It is strongly recommended that the sample data be investigated for any explanation of this variation, whether geological or process related. In the interim the average grade of AK8 is estimated at 7cpht at a bottom cut off of 1.0mm.

AK8 - Detailed ground gravity model

Modeling of the results suggests that the average diamond grade for AK8 is approximately 7cpht, but that the complex internal geology and the presence of internal waste, suggests that parts of the pipe may be of higher grade.




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