What this place is
At Mponeng the rock is around 60 C before any machinery starts, and the mine ships ice underground by the tonne to make the air survivable. It is the physical limit of how deep humans currently mine.
Grade. Narrow, high-grade reef — a seam sometimes thinner than this line of text.
“Grade” is the percentage of the useful stuff in the rock. A copper mine at 0.5% grade throws away 199 tonnes of rock for every tonne of copper it sells. That single number decides whether an orebody is a mine or just an interesting piece of geology.
What comes out
Gold
The metal that does not tarnish, does not corrode and never runs out once mined — which is why almost all of it ever…
Uranium
A heavy, faintly radioactive metal whose nucleus can be split, releasing about two million times more energy per…
A “by-product” is a metal recovered because it happens to be in the same rock, not because anyone went looking for it. Its supply therefore follows the primary metal’s economics, not its own.