A trillion-tonne threat hangs over critical minerals

YOU might think that the business of mining is digging up valuable minerals. In fact, it’s almost the opposite.

Most of the rock that miners blast, shovel and truck out of the ground is useless waste – first the overburden of worthless material that has to be dug away to get to the ore body, then the tailings left over when the ore has been ground up and processed to extract its useful elements. To produce a teaspoonful of gold these days, you often need to remove an Eiffel Tower’s worth of material from the earth.

Managing that growing mountain of dross – likely more than a trillion tonnes at present, and forecast to double by 2050 – is one of the biggest obstacles to getting our hands on the critical minerals that the world will need over the coming decades.