If I view the image you posted correctly, my conclusion in that case would have to be modified. God made the cube, and you are God.
Am I close?
hehe I could feel those goalposts flying by before you even posted!
Closer than a lot of your other conclusions, certainly.
No. They're just pyrites crystals. They're perfect cubes, and they're common as dirt in some parts of the west.
If anything or anyone made the crystal it was bacteria. They reduce sulfate to sulfide; that then combines with iron, and slowly crystallizes. It's tough to think of bacteria as intelligent designers.