Understanding Pilbara conglomerate

Dear fellow holders- I am looking to invest a bit more in this gold rush -
though coming from non geologist background- I feel I lack some understanding of the basic problem here -compared to other gold areas-

So conglomerate means a lot of little stone pebbles and then now and then a big gold nugget-

Now for my understanding of this conglomerate story - drilling could probably underestimate the gold per tonne if they don't hit the nuggets exactly ??
How do you estimate this resource if it consists of a few 15 cm large chunk nuggets and plenty of dirt in between without any gold?

I feel simple drilling could potentially result in serious underestimation of the gold per tonne - true

Please dear geologists -in plain English -how do we actually estimate gold per tonne in conglomerate ?