Since the start of large-scale mining operations, mineral processing techniques have seen huge improvements. Because of this, tailings from older operations can contain mineral quantities high enough to make reprocessing of these tailings economical.
Several large mining companies have realised this and have started reprocessing tailings. De Beers, for example, have recovered millions of carats of diamonds from tailings surrounding the Kimberley mines in South Africa.
Due to different market demands, minerals that would have been uneconomical to extract when they were mined as a by-product could now be profitable. Rare earth elements are a good example – because of their increased use in modern technology such as smartphones and tablets, the demand for these rare elements has risen significantly.
Several companies specialise in obtaining old operations to reprocess the tailings. Generally, the longer the operation has been closed, the higher the potential returns from the tailings. This is because older recovery techniques would have been more primitive, and material containing grades that are economical to extract using current processing techniques would have been rejected.
Assessing the economic value of tailings requires a good understanding of:
- the contents of the tailings
- what processing techniques are available to effectively extract the targeted minerals
- what additional infrastructure is required to transport tailings and perform the extraction.
Environmental concerns need to be considered prior to obtaining a site. Older operations especially often have historical environmental issues, which can be very costly if a company is held liable for the mitigation of these issues. On the positive side, reprocessing tailings can have a favourable effect on the environment, as potentially harmful minerals can be removed during reprocessing, ensuring they can no longer leach into the environment.