My friend let me introduce you to the terrifying process of cyanidation, wherein finely crushed ore containing traces of gold is made into a slurry by adding water, then transferred into vats known as “slime separators,” where potassium cyanide is then added to leach the gold into a liquid. Slaked lime is used to prevent the cyanide from going into full Murder Mode as hydrogen cyanide. The gold is then separated from the cyanide through one of a series of processes that I’m not really qualified to explain, but I think there are a few websites that talk about them if you want to google them.
But the key point here: from what I can tell, cyanide has been the main method of getting gold out of the ground for the last 120 years. (Yes, this process is still used today.) Before this technology came along, instead a thin coating of mercury was spread onto a copper plate, and the ore was allowed to wash over it. The gold stuck to the mercury, creating an amalgam, and then the amalgam was scraped off the plate and the mercury was boiled off (urk) to leave the gold behind.
And when processing mills shut down historically, why bother to dispose of your leftover deadly chemicals properly, when you can just bury them in your local tailings pile, which is already contaminated with mercury and arsenic? The known case of this happening in my local area was revealed through a bloom of “Prussian Blue” (ferro cyanide) on the surface of the tailings. Luckily, this is a fairly stable form of cyanide. Unluckily, geologists are crazier than archaeologists and they went ahead and dug a sample test unit right next to it, even knowing what it was, because science.
When I said to myself, “I’ll be an industrial archaeologist. It’ll be cool,” I did not foresee the terrifying knowledge it would unleash upon me.
