Mineral Processing

Concentration Steps

Copper ores usually contain from half to a few percent copper, the median now being around 0,6% percent. The copper mineral itself would then consititute a little bit more since other elements are bound up in the mineral, typically around 2% of the ore sent to the mineral processing plant. The remaining 98% is what is called gangue minerals and the ore dressing plant's purpose is to remove these and refine the copper bearing minerals as much as possible. Though copper producers continuously search for alternative markets for the gangue minerals, often silicates or oxides, these are often valued so low that they cannot be sold.

The first stage in copper concentration is liberation grinding (called comminution). Typically the copper bearing minerals exist within the rock as grains of a particular size. The rock then has to be crushed down to "liberate" these copper mineral grains so that they can later be separated from the rest of the minerals. The grain sized can often be in the ┬Ám size. The smaller the more difficult it can be.

The second stage is to separate the liberated ore from the gangue minerals using a set of mineral processing tools. The most common separation techniques are:

  • Gravitational separation (using the fact that copper minerals often are heavier than the gangue minerals, mostly used on the very rare native copper deposits)
  • Leaching (a metallurgical process dissolving the copper bearing mineral in acid and then extracting the copper from the dissolution)
  • Flotation (also called froth flotation, floats copper bearing minerals to the top of flotation machines with the help of chemicals that binds to the surface of the minerals and then attach to bubbles (the froth) in the machine).

Which method is used depend entirely on which minerals are present and other ore parameters.