Twilight, you ask good questions. The challenge for you will be to understand the answer, because it's not obvious.
When you took out the highest grade interval from the mineralized segment of core, why did you pick that specific interval? Why don't you run the same calculations, but drop each single assay interval sequentially, and see what kind of numbers you get? What you'll find is that you'll get only one average grade across 33 metres of the 34 metre interval that has a low grade, the one you chose to calculate. What you've done is arbitrary. The gold is randomly distributed in the diorite, so picking that one single 1 metre interval to exclude from your statistical reinterpretation has no basis. If you randomly leave out a 1 metre interval from your recalculation, the vast majority of the cases will give you a similar average grade to that reported by the company.
The head grade is the average grade of the bulk material that has been mined. There is no a priori method to determine where the nuggets will be found. The best you can do is to determine a volume of rock that you believe to be mineralized (called the envelope), and you mine all of that. If your grade estimators are at all accurate, you'll be mining at the average grade you determined via sampling, i.e. your head grade will be similar to your grade estimate.
It's not yet absolutely clear, but it is a reasonable approximation to suggest that you would mine all of the quartz/diorite breccia, and perhaps also some of the quartz in the sediments. Because some sections of the quartz/diorite breccias are very wide (70 metres? at Snow White), and longer than they are wide (length not yet known at Snow White, but 200-300 metres at Timmins, so far), the underground operations would be very compact indeed. We won't be following narrow veins, as it would appear to me that you are assuming.
Lar
