RE: Recent take over prices9 Apr 2021 18:37
Steve, it is an interesting and relevant fact that Racecourse is tipped over on it's side...this imo is a positive for the open pit mining, but a negative for the underground possibilities. Open pits usually stop at about 300 metres-ish, because beyond that you're increasingly spending your efforts moving too much worthless crap for every ton of paydirt. Some can go a lot deeper, due to the grade, the geometry or the processing route. But 300m is a good rough guide.
But when the pit stops, the underground mining methods must begin. But even the bulk methods like caving do have a much increased cut-off due to the greater expense regime. Grades that work in a 300m deep pit may not work at all for any sort of u/g scenario.
And the geometry of the mineralisation is crucial. If the orezone drifts off sideways, then you can't just build a big drawbell and collect it all caving for the next 50 years. Instead, you will have to replicate this big risky capital expenditure many times moving laterally...also know as ****ing money up against a wall.