Well, it's pretty rickety, but I'm guessing it's an ore bin rather than a fallen down headframe because it isn't located over (or near) an old shaft, unless the shaft has been buried by a later mine dump, which -- given the non-square nails in the thing -- seems unlikely to me.
After taking the photo, I climbed the angle-of-repose dump, cemented and hard to get any footing in, by grabbing a buried cable and pulling myself up step by step. Gloves would have been ideal for this undertaking, but I didn't have any with me. Not something I carry routinely out in the field, although there should be a pair or two somewhere in the back of my truck. Up at the top of the mine dump, the signs of the old workings that led to the creation of the mine dump were quite vague.
Oh, and I found some wildflowers, too.