Evidence based speculation, page-40

I do not know why they do not need to use Hydrochloric acid , but maybe there is sodium chloride (common table salt) n the ore already , I really do not not in fact know why they need to use Nitric acid rather than using an autoclave and heat as like you I am not a metallurgist or chemist .
All I was working out was the amount of energy to melt one tonne of the ore which I had the ability to work out for you as it seemed a reasonably basic calculation and comes out at less than the cost of 2 grams of Au.
It would seem cost effective to smelter Au for ore that was say 6 grams a tonne .
, prefer if you refuted or corrected that than ply me with other questions that I have no knowledge in answering as at least then we would be able to nut out the correct cost of energy for smeltering a tonne of ore .