It used to be that high grade gold mines like Kirkland lake mine where the way to go to make money in metals. I never believed it was that easy, as KL was even not making money at 200k/year, due to high costs involved, so even high grade underground mines need size and very high grade in order to make decent money.

Only KL is making strong free cash flow from underground mining, all other mines that make big money are low cost, big open pit mines:

https://www.mining.com/ranked-top-10-lowest-cost-gold-mines-globe/

See what happens today at HRT and last week at PVG and TMR. I prefer to bet my money on simple low grade open pit mines. Exemptions however are WDO (still advancing its second mine) and KNT (in Papua Guinea)