NST - Valuation and SWOT August 2019, page-6

Interesting that, isn't it? NST has higher grade gold, but EVN has longer reserve life and AISC margin. I think what happened was Pogo really hit NST in the past year given they have had to spend quite a bit on capital expenditure.

And that being said, EVN has a number of open-pit mines that have lower ore grades but they have taken advantage of the economies of scale.

Most of the time, underground mines with good ore grades would have lower AISC and hence higher profit margin, but EVN and RRL are indeed exceptions to the rule.