When I was a younger and more sprightly woman, I spent part of my life investigating unusual hot springs in rural California. They were salty and quite stinky springs out in the middle of nowhere, and several of them occurred right in the center of an old gold-laced mercury deposit. No one was actively mining the small area where the springs are found – there just wasn’t enough ore to make the project economic. But the rocks of the location had small veins of chalcedony, calcite and other minerals that had elevated values of both gold and mercury in them. Working with a couple of colleagues, I took samples of the spring waters, the gases bubbling out of the springs, the precipitates forming around them, and anything that looked interesting in the nearby rocks.
The fieldwork had its challenges. In the afternoon it was routinely over 100 degrees, and the sun was relentless. One afternoon I even flirted with heat stroke. Another problem was that the rattlesnakes were numerous and big.
I spent a lot of time in the laboratory back east analyzing the waters of the springs. They were transporting gold, and the question was how. Gold is normally quite insoluble – that’s why it can be used to crown a tooth. Even in an environment rich in warm spit and sips of hot coffee, a golden tooth won’t dissolve away because gold is quite insoluble under most conditions. But clearly the hot springs were different. In the end, I concluded that sulfur in the spring waters was keeping the gold in solution until the waters broke to the surface and the gold precipitated out as temperature and gas concentrations changed.
There were some other interesting things about the strange springs, too. Some of the cooler ones had the larval stage of an insect living in them. I took samples of the wiggling little creatures and gave them to a biologist to identify. The insect normally lives around the ocean in salt-marshes, but it was making use of the salty springs even though they were well inland.