>> Excuse me....100 meter deep overburden would more likely encourage an underground model if grades merit costs.Not all diamond mines are open pit...;) <<
Good point, & I certainly don't argue it, Eder. If the grade seems to merit it, the question is then the makeup of the region's geologic strata, in terms of it being competent to support an underground mine (ie, whether it can or not):
Boulay stated,
Also, the soft Cretaceous mudstones will not likely form an effective crown to permit underground mining and the rocks themselves probably lack the integrity to support a mining operation at acceptable costs. Big unknowns. (Nov.13)
And,
Ideally both underground and open pit examples would be best. However, the incompetent upper Cretaceous mudstones could not likely be used as a crown pillar (i.e. a mine roof) and the soft rocks would probably lack the integrity to allow underground mining at any grade. We have only performed rudimentary calculations on underground thresholds and they are not worth refining into exploration model thresholds. (Yesterday)
It's not a matter of playing any 'card' as has been ignorantly claimed by JP. It is a component of the area's geological makeup, and a legitimate concern that will have to be dealt with by all exploring, from both a physically possible perspective and from an economic perspective.
regards,
-j
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