CURWOOD: So, in your article, in the magazine On Earth, you write that the days of a miner panning for gold on a river and coming up with a shiny nugget are over. They’re after much smaller amounts of gold, flecks of gold, in Peru. How do they get the gold from the Earth around it?
BLACK: That’s really the problem and it’s why these mines have grown so enormous. What you have now is literally fractions of an ounce of gold for every ton of rock. And what that means is that the rock is crushed into small, pebble-sized chunks. You pile those into mountains that can be hundreds and hundreds of feet high and then you snake pipes up the size filled with cyanide, sodium cyanide solution, and that drips down through the rock in a process that can take months. And cyanide has the property of being able to coalesce the fragments of gold into a sort of slurry that then collects in a pit at the bottom, and then that is processed and purified and then turned into gold ingots
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