Tailings and other mining waste and how it is handled

Mining waste is generated in all mining operations. They can be divided into several different parts, the most significant of which are:

• Waste rock
• Tailings
• Mining drainage water

All mining activities generate waste rock, tailings and mining drainage water. The quantity and volume can vary greatly between different activities, depending on the type of rocks and concentration of element(s) being mined as well as the mining method (open pit or underground mine).

Waste rock

Waste rocks are rocks that are mined to access the ore deposit (the mineable part of rocks that is financially viable). Waste rocks are present in both open pits and underground mines. They are typically stored in the vicinity to the mine and is generally covered with several layers of soils with various grain size and composition or redeposited in the open pit or underground mine upon completion of operations, the latter is referred to as remediation or land reclamation. In several cases, this occurs continuously during the operations, referred to as progressive land reclamation and remediation.

Read more about gangue

Tailings

Tailings is generated after the ore is crushed and processed into a ore concentrate that is often sold to smelters for further processing. The remaining product is referred to as tailings and it is another form waste material which is typically very fine-grained. The amount of tailings that is generated is proportional to the content of valuable elements taken from the ore. A low content of valuable element results in huge amount of tailings; while a higher concentration, for example, as in the case of ‘bulk commodities mines’ such as iron ore mines, where iron content may exceed 40 percent, less waste is generated as tailings per tons of processed ore.

Commonly tailings are stored in Tailing Storage Facilities (TSF), which are structures designed to hold the sand. In some cases, tailings can be used for filling rock rooms.

Read more about the enrichment process and tailings

Mining drainage water

Mining drainage water consist of water used by mining operations in various processes, runoff water (e.g., rain), surface or groundwater that interacts directly with the mine or with mining waste. Mining drainage water that exits mining operations, via a tailings pond, can be regarded as a kind of waste. The environmental permit must contain information on the concentration of metals or other elements that such water may contain when it exits mining operations and it is discharged in nature. If necessary, mining operations may need to construct a water treatment plant that remains in operation until land reclamation related to the mine has been done or until mining drainage water has achieved stable chemical conditions so that the environment is not at risk of harm at the time it is discharged. Mining drainage water is often recirculated several times in the operations, for the purpose of minimizing the use of water.

Read more about water, environment and human health