My opinion is that the 'Glory Hole' is a red herring as far as the likely gold grade is concerned, for a number of reasons.
Firstly, gold is incredibly 'nuggetty' in its distribution and rapidly changes tenor over very small distances. Imagine the original drill hole with a diameter of 4cm or so; the very high grades were only found over a 1 metre sample length within that hole. 450g/t only equates to 450ppm (1% = 10,000 ppm); at these levels analytical certainty drops off quite markedly as most techniques are geared to lower, more common, grades and the potential for sample bias is increased dramatically (gold is very difficult to prepare as analytical samples, due to density issues and the low concentrations involved); ensuring efficient mixing and riffling when you are only going to analyse 30g or less of the original sample is essential.
Secondly, you're dealing with a shear zone. It's difficult enough to extrapolate gold grades in a vein; but in a shear any ore shoots are sliced and dissected so that there is little or no continuity. Admittedly there has not been any information forthcoming from the company as to the orientation, nature or frequency of the shears; but these are very often fractal systems that can be traced at the microscopic level as well as the macro. Hitting that high grade pod was a fluke (the rest of the grades in the hole attest to that) and it is very possible that the drill simply intersected a very rich pod the size of a tennis ball, in a mass of potentially barren material. A shift in the drill hole a few cm in any direction and you would never have seen those grades.
Thirdly, you have to consider what you are trying to achieve. When you have a single drive with a whinze here and there you can pick the rich eyes out of it, but you'll have a very small tonnage of ore to offset against your development costs. Ideally you want to put in further levels and mine out the panels between them, but here high-grade spikes are irrelevant - only the average grade of the material you extract counts and even then you will have to keep it above 10g/t or more to make any money - working underground is expensive - working within a shear zone doubly so in terms of ground support (look at the whinze an the support it needed) and combatting dilution from the wallrocks and low-grade areas.
Any development is useful as it furnishes more information and it is better than drill core because you can stand within the rock mass and see it in three dimensions and take appropriate measurements, etc (it would be nice to see some detail from the geo's working there); but trying to extrapolate within a shear is difficult enough, never mind deeper into the mountain itself. Such assertions have no scientific basis whatsoever, nor do claims based on the idea of 'average porphyries' (the next time I meet up with Richard Sillitoe I'll run that one by him). There is no substitute for diligent fieldwork using all the techniques you have to hand and basing your assumptions on hard data.
AI
