Anyone know what's nearby there at about (32.92669, -111.922201)[0]? It looks like some sort of strip mine a few hundred feet to the north, so I assume it's related, but was just curious what it is. It looks like a painting!
As e2021 said, these are some kind of tailing dams to treat remaining water from mining.
Google even has streetview photos from the nearby road, resolution is just enough to read "[something] wastewater evaporation ponds" on the fence sign: https://goo.gl/maps/WZKbdPxs5sS2
Looks like a tailings dam to me, containing waste materials from the mine after processing. The solution has partially evaporated leaving a salt residue.
At least thats what it looks like to me. I don't think its a raised pyramid like the other reply says, pretty sure it is a hole.
If you do a google image search for 'tailings dam' you see some things that look pretty similar...
Looks like some kind of debris pile, perhaps from the mine. The corners are angled like it's building up to an eventual truncated pyramid shape, and the one in the upper left looks higher, and "finished" compared to the other three. There's a similar pile that isn't laid out as a square just south of the mine, you can see the multiple layers getting smaller as it gets higher.
Google even has streetview photos from the nearby road, resolution is just enough to read "[something] wastewater evaporation ponds" on the fence sign: https://goo.gl/maps/WZKbdPxs5sS2
The mine itself looks cool, too: https://www.google.cz/search?q=Casa+Grande+Copper+Mine&safe=...