I asked Tilsley that question and he (and Dany) explained to me that the chaotic nature of the quartz mineralization in diorite can sometimes produce mineralized structures that terminate abruptly in the vertical axis without any warning. Therefore, it seems that coming across strike gives a much higher hit rate (like the broad side of a barn door analogy). Tilsley did agree, however, that if you could drill a hole through mineralized quartz all the way down to 300, 500, 800 m etc it might reduce the nugget effect somewhat and give you a better idea of the grades for that part of the deposit.

Best,

Scott