Processing Track: Mineral Processing, Refining and Recycling · Module 1 of 4 · about 15 min
Crush, grind, separate
Ore comes out of the ground as rock with a small amount of valuable mineral locked inside. Processing starts with comminution: crushing, then grinding, until the valuable grains are freed from the waste rock. Grinding mills use a lot of power, and comminution is often the biggest energy cost in a concentrator.
Once the grains are free, the plant separates them. Froth flotation is the workhorse for copper, lead, zinc and many other sulfide ores. Reagents make the target mineral repel water so it sticks to air bubbles and floats off as a froth, while the waste sinks. Gravity separation uses density, and magnetic separation pulls out iron minerals.
The output is a concentrate, which is richer than the ore but still not metal. The waste is tailings, which go to a storage facility that has to be engineered and watched for its whole life.
Plants track recovery, the share of the valuable metal in the feed that ends up in the concentrate. A recovery of 90 percent means 10 percent of the metal went out with the tailings. Operators chase recovery and grade together, because pushing one too hard usually hurts the other.
Sources
Module quiz
5 questions, 4 correct to pass. You'll see what you missed and why, and you can retake it.