Today's photo comes to you from atop a massive rock-and-brick structure: the Tamarack #3 hoist foundation. The Tamarack mine was, once upon a time, the deepest mine in the world. The Tamarack shafts were so deep that they were used by physicists at MTU to attempt to measure the effects of gravity deep within the earth.
Nowadays, very little is left. This particular ruin is made up of massive cement and poor rock walls, lined with bricks (for heat resistance). Over time it has been ground down into dust and chips -- and this is the result.