Historically, the crushing, sifting, and sluicing was the way to go. They still use cyanide to extract gold, but it’s done in a much more enclosed manner. For instance, they’ll put a bunch of crushed rock in huge vats, leach it with cyanide, recover the product, and then either recycle the cyanide or send it through water treatment. Tailings are then stored in a tailings storage facility. For some low-grade ores they’ll use an acid heap leach, where they take ore, and pour sulphuric acid over it. I’m not a mine process engineer, but I do know a bit having worked in the industry indirectly.

Env. and human health concerns are always important. Mostly what I wanted to show with this article was that there’s sometimes a chance for remining and that can be a good thing in some cases - in this case, they got rid of a waste pile and likely put it further away from people.