Take Lundin’s Bonza Sur drill hole BLP-2026-553, for example, which intersected 204.26 grams per tonne (“g/t”) of gold (“Au”) over 3.05m from 140.25m, including:
- 1035.60 g/t Au over 0.60m
Naturally it’s exciting to have the kilogram per tonne resource, but:
3.05 metres at 204.26g/t = 622.99 g/t per metre (3.05 x 204.26), and for the same assay,
0.60 metres at 1035.60g/t = 621.36 g/t per metre (0.60 x 1035.60)
So the result is really a two foot long section at 1035.6 g/t plus eight feet at 0.5 g/t for ten feet overall mineralisation. Applying the same arithmetic to the other three results shows that really only the smaller numbers are relevant. So the practical results, including the down hole distances, are:
BLP-2026-553:0.60 m @1035.60 g/t from 140.25m
BLP-2026-483-D1: 50.44 g/t Au over 2.30m from 698.30m
BLP-2026-483-D2: 23.21 g/t Au over 3.20m from 715.35m
BLP-2026-475-D5: 179.0 g/t Au over 0.40m from 962.45m
which is all indicative of a veined resource, which they say is indicated, in quartz. Which is refractory.
Those are four results from 20 holes drilled, the other 16 having much lower or insignificant grades at various depths.
Next you need to look at the locations, and the angles of the drills. Two holes drilled half a metre apart in the same direction both intercepting a kilo/tonne of gold is the same as one hole, but two great results. Two holes drilled half a metre apart in the same direction with one hole reporting a kilo per tonne and the other zilch is typical of a narrow veined quartz resource. A nightmare to prove up a reserve which is necessary to get finance, but not necessarily difficult to mine as you just follow the vein until it is exhausted – depending on how deep it is. Two holes 100m apart angled to meet where the gold is may provide useful data for a mine design, but gives brilliant marketing ammo for the share brokers.
And so you build up a profile of the deposit, always looking for what they aren’t telling you.
Then you’ve got all the usual things for a mine, permitting, location and accessibility, water, energy, politics (Mali was OK ten years ago), EPA rubbish etc. etc. Oh, and time scale.
It’s not difficult, but it is time consuming, and you get better the more you do.