Tailings...a sustainible source of metals for future generations?

"Miners are often seen as agents of damage, but when there are positive attitudes at play, tailings projects can offer the opportunity for companies to change that by providing communities with solutions for problems created in the past."

One of the sources of concern often raised about new mine development is the impact of tailings. First some background information and definitions. Metals occur as minerals in rocks. In order to separate the metals from rock, the rock first needs to be blasted, crushed and finally ground to powder. The metal-bearing minerals are then separated from the rest of the powdered rock. The methods for separating the minerals desired from those unwanted depends on the minerals in question. Usually the powdered rock is mixed with water and in the resulting slurry, the minerals separated using chemistry as every mineral has unique chemical and physical properties. For example gold can be separated from rock simply using gravity as the gold particles sink to the bottom of the slurry given that gold is denser than the rest of the slurry. When the metal has been separated what remains is ground up rock and water. This is what we call tailings. Since most metals occur in very low  concentrations (for example rock economic to mine for copper average about 0.5% copper) by volume much more tailings material is produced than metal, which then is stored on the minesite.

For almost all metals our current level of technology does not allow us to remove 100% of the metal out of the rock and, in the case of copper, usually only about 80% leaving significant amounts of valuable metal in the tailings. But we are getting better and more efficient all the time. We are able today, with technological advances, to mine much lower concentrations of metals than before because we can get more of the metal out of the rock than was possible in the past. That is why many companies return to old mine sites to re process old tailings as described in this article. In the process the old tailings are cleaned and rehabilitated in a modern fashion. If the technology exists to get out the remaining metals, tailings can be cheap to re process. This is because much of the work has already been done as the tailings have already been mined, blasted, crushed and ground. They are ready to simply re process when the next technological breakthrough comes along.

Tailings piles can be reclaimed and returned to nature as we have discussed in these pages. In fact most government legislation mandates this. But are we missing something? Rather than viewing tailings strictly as permanent blights on the landscape requiring reclamation, is there not another way of seeing them? Might they not also represent a valuable repository of metal for future generations? After all, a lot of societal energy was involved in creating them in the first place and mineral recovery technology is improving rapidly. Just as yesterday's tailings are economic today, surely tailings we create today will be mined sometime soon?