Milling ore is the extraction of metals for the highest financial return. To recover the maximum amount of precious metal, the ore must be finely ground to liberate the particles for gravity separation and/or chemical extraction.

The extraction of minerals from ore can be done in two ways: placer mining, which uses water and gravity to concentrate the valuable minerals, or hard rock mining, which pulverizes the rock containing the ore and then relies on chemical reactions to concentrate the sought-after material.