Going underground...

　
This blog is credited mostly to Bob, since it goes into geology that I can comprehend but not communicate!

We’ve talked about the unique and varied geology of the Black Hills. The Homestake Mine, active in the Black Hills for over 100 years and now committed to an underground science lab, worked underground as well as open pit.

We were lucky enough to play host to some geologists who were very interested in the Homestake and thought we would share some of the information we have accumulated on the subject.

Here is a 3-dimensional model of the Homestake formation.
　
We were lucky enough to have an underground tour before the mine closed and are grateful that happened. It’s was awesome, hot, humid and amazing all at the same time! The tour started (after a safety orientation) with a ride down the Yates shaft to near 5000 feet. We continued to the #4 winze shaft which took us to about the 7000-foot level, then walked to below 8000 feet. It was an experience I don’t know if I’d want to repeat, but definitely a chance in a lifetime!

This diagram shows the plunge and complex folding of the underground workings.

The geologic makeup of the Homestake is shown below, but the majority of this is visible in the historic Open Cut as well.

What is equally impressive, though (as portrayed by red dotted line on topo below), is how much underground real estate was developed. We know they went 1-1/2 miles into the ground, but how many surface acres were involved? This map gives you a rough idea, though it is by no means a true model. Work was most concentrated in the Lead area, but progressed to the southeast with depth. Strawberry Hill, if you are familiar with local landmarks, marks what might be the southern boundary of underground activity.

So the open cut, though huge, is just the tip of what happened underground.

We always enjoy talking to the old Homestakers; do they have stories to tell!