When I was on the site visit Tilsley was asked this exact question. He basically an even wider dirll would be still too small a sample to get an accurate grade. At some point we will either get to do bulk sampling at the surface if we are really lucky or we will have to make a shaft and take a large diameter core out. Underground bulk sampling - we could have to do both. All doable but cost money. From the shape of Tisley's arms I would estimate around half a meter in diameter was his estimate for the core size needed but I could be off by a factor of 10 or more.
There is some equation for getting to use a bulk sampling for estimating grade.I probably have this number wrong - 16 instances of gold per sample in order to obtain an accurate grade. Anything less than that and your statistical sample size is too small and you need more material to get the grade. that number might not be 16 it might be 32 for all I know but Tilsley had an exact number needed. All of this stuff is doable...
We use the drills to find the resource that is in the quartz an diorite and to determine tonnage and then bulk sampling to determine grade. Just what we will have to do... Takes more time costs more money... but a problem that is easier to solve then lets say having no roads for 100 km.
