The town of Lead, SD, pronounced “leed”, is home to the Homestake gold mine. The mine was purchased and subsequently developed by George Hearst, father of William Randolph Hearst, and partners ca 1876.
The photo above shows one ground view of the large open cut found on the north end of town. The pit is approximately 1/2 mile across and 1200 ft in depth from the highest elevation.
The pit exposes the ore body which is comprised of inhomogeneous igneous rock with gold bearing veins. In the photo below the vein structure can be seen. The buff colored rhyolite bands seen below are not associated with value.
Gold was discovered at a surface exposure, called a “lead”, which became the namesake for the town of Lead. Mining activity was halted in 2002, in part due to the low price of gold at the time. By that time the underground workings had reached a depth of 8000 ft, which puts it at ca 3000 ft below sea level. The rock temperature at the 8000 ft level was reported to be 130 degrees F, requiring substantial air conditioning for the workers and equipment.
The (poor quality) photo above shows the hoist equipment in the Yates head works. Of interest is the conical cable spool used to provide lift for hoisting operations at the Homestake mine. The purpose of the variable diameter feature of the hoist was to provide maximum mechanical advantage when the cable was at the end of its reach, presumably when it was ready to lift a heavy load of ore from the bottom of the shaft.
The “ore cart” in the photo above was the toilet facility for the miners. It featured a seat on top which could be sealed, a thoughtfully placed foot platform, and railings so the user could hang on for those rough rides.
The surface tour of the mine consists of a trolly ride around town with a stop at the Yates hoist. Warning: It is quite superficial in content, but is the only type of tour available. Our tour guide was student on summer break with near-zero knowledge of the geology or the engineering. He was accustomed to entertaining the barely interested. If you are keen on the particulars of Homestake history, I recommend Nuggets to Neutrinos, by Steven T. Mitchell.
Homestake was one of the very richest loads of gold in the western hemisphere. Reportedly, some 40 million oz of gold were extracted from the mine.
Today, the Homestake mine is being converted to an underground nuclear physics lab facility under a program called DUSEL. On a side note, it is interesting to listen to the townsfolk talk about the new labs. I could tell they are trying to be enthusiastic, but the reality of neutrinos is very hard to get your arms around.