These are part of the possible reserve category. It this situation, the veins were identified in outcrop or trenched exposures (188), sampled in enough detail to provide a grade estimate, but not in enough detail that a geologist or engineer would accept as measured....it is only indicated. Faults, pinching and swelling, or any other variation could change these numbers. In the case of the 188 vein, the Russian/Mongolian workers drilled the vein and intersected it at depth. We accept that there is a vein down there, and feel that it is reasonable to consider it to be the 188 vein, but will not consider it proven. We then must determine if we are comfortable with calling it probable or possible. We opted for the lower classification...possible.
As far as analysing these results, most analysts will consider proven or probable reserves. Few place any value on possible reserves, other than to be used as an indication of hope for expanding the proven and probable categories.
The proven and probable resource numbers would normaly be discounted several times. First, a determination has to be made "are they accessible, or can they be mined?" This question need to be coupled with "how do you propose to mine it?" Once this is determined, a suitable dilution factor, representing the amount of waste rock that inevitably gets mixed in with the reserve has to be considered.
Only once these, plus some milling and economic factors are taken into account will you see a resource referred to as "ore". Often with many adjectives such that you get a "diluted ore reserve".
Our experience at Bumbat, is that we have been mining the same number of ounces that our reserve figure indicated, but more tonnes at a lower grade. This is due to more dilution coming from the mining than planned or expected (as reported previously). While it is not too much more, every tonne of waste we do not mine, or do not mill, saves us money. We are looking at why the dilution is what it is. Is it the nature of the ore, or is it a poor blast pattern, poor loader operator, poor sampling, mistaking a truck load of waste for a truck load of ore, and on and on? We have been able to identify several reasons, and are looking for others. I think we have a better understanding of the operation today, and we're looking at incorporating these changes into the plan.
Dave |
