I think I have posted this link before. https://castledomemuseum.org/mines.html
One mine has a shaft 700 feet deep. That is straight down, not the usual slanted shaft where you can walk in and out. Access was by an elevator platform suspended by a cable and powered by a gasoline engine on the surface.
There has always been somebody trying to turn that portion of the desert into a tourist attraction. The town described at the link was at one time the site of a religious retreat, and before that there was a long list of people trying to finance something or other. So that is why there was some curiosity about what was at the bottom of the main shaft.
The only thing I remember about the trip was a mason jar imprisoned in flowstone. Water at that level is as much rock as liquid, mostly calcium, and it flows over things and dries to produce an iridescent white rock. With a mason jar trapped in it. The humidity there was surprising. Also surprising was the cool temperature.
A couple weeks after that trip, some punks snuck in and tried to steal an ore car out of the shaft. They got the hoist running, located a car, rolled it onto the elevator platform ... and the cable broke. The same cable that we had bet our lives on just a couple weeks before. I have no idea what happened to the punks.