What this place is
A single district in Hunan has anchored world antimony supply for more than a century, which is why export restrictions there move the global price immediately.
Grade. High-grade stibnite ore.
“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
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.