We ramp up into a potash seam. Neil brakes the van to a halt in a swirl of dust, jumps out, cracks a fat flake of potash off the tunnel wall and hands it to me. It is pink as meat and flecked with silver mica. It is surprisingly light, almost buoyant in the hand. ‘Lick it,’ says Neil. It fizzes on my tongue. It tastes of metal and blood. I want to eat it all.
