Great shot! I remember slag heaps along a highway near the town where I grew up. They eventually leveled them and built a mall there. The heaps you've photographed here look far more attractive surrounded by all of that natural beauty than did the heaps along the highway that I remember.
Wow. The town I grew up in was surrounded by coal ash from the local zinc factory. They have cleaned it up in recent years and I hardly recognized the place the last time I visited.