Sorry to disagree, but your statement about the visible gold in the drill core is not accurate. If a core with VG is assayed and returns insignificant values, then it's because the VG didn't make it into the assay (likely left in the other half of the core, which is retained). For the sampling size to be large enough to be representative of the actual deposit, bulk sampling is required. Drilling, in this case, serves to define the mineralized area, but does little to accurately define grade.