An internet search of the phrase "mine tailings" will return a veritable litany of websites dedicated to the potential liabilities of mine tailings. But should we only be thinking about mine tailings in the negative? Could tailings not also be a societal asset? The USGS thinks so as they are looking for valuable and strategic rare earth elements in the tailings of old mine sites, where other metals were the reason for the past mining.
Tailings refer to the rock that remains at the mine site after the mineral sought has been removed by a process plant located at the mine site. Typically processing plants crush and pulverise rock in order to more readily remove the valuable minerals from the rest of the rock now called tailings. Enormous amounts of energy go into crushing and pulverising the rock during the mining process. At the same time even modern mine processing plants cannot recover all the metal in the rock mined. For example in porphyry copper-molybdenum deposits from which approximately 50-60 percent of the world’s copper, and 95 percent of molybdenum comes from, recovery rates for both metals are rarely above 90% and historically they have been much lower. This means that tailings worldwide contain a tremendous readily available metal resource for future generations who will almost certainly have developed means of extracting the remaining metals that we currently don't possess. This is precisely what the US government has undertaken to find out with respect to rare earth element metals they consider geopolitically strategic. Unbeknownst to the operators of long shut down gold, silver and copper mines there are also concentrations of rare earth elements in the rock they mined and the tailings left behind. The discovery of these metals, vital for many modern electronic items, means that long forgotten leavings are now of value. What makes these tailings now valuable however is the energy that has already been expended to crush and pulverise the rock they are made of.
There are many people who focus their attention on the perceived liabilities of mine tailings. The focus of their attention may be so negative that they cannot see the potential asset in front of them. The 20th century has brought many new mining technologies to bear which have allowed the profitable reprocessing of pre 20th century mine tailings. Our guess is that this trend will continue: tailings created today will be mined profitably tomorrow. The entrepreneurs of the future who identify these opportunities wont be the people who view tailings only as liabilities.