Mineral processing is the activity of separating commercially valuable minerals from the ‘waste’ rock (gangue) that encases them. The crude ore is subjected to comminution—crushing and grinding to reduce size—and concentration of the usable mineral by various means of separation, including froth flotation or centrifugal devices.
The largest amount of energy used in mineral processing is in the comminution phase. In some operations, the grinding phase of comminution can account for as much as 70% of total energy used and greenhouse gas emissions produced from the mining and mineral processing process. Globally, most comminution energy usage occurs in the processing of iron ore, and of the non-ferrous metals, copper and gold.
Additional energy is needed to mine and process ore grades of declining quality. As well as being less profitable or cost-effective, this situation increases the embodied energy of primary metal production and the associated greenhouse gas emissions. These consequences are especially significant for the most production-intensive metals, like copper, gold and nickel.
It is important to take a holistic approach to keep mineral ore concentrations, beginning with the resource characterisation stage.