I deal with rocks in bulk. We pick them up rom the fields and deposite them in disignated piles on several farms. Some times the county will take them for a project and some times private folks come and sort through them and take some for landscaping projects. Mostly they are a pain in the rear. One thing about them is you only have to move them once.....
Ocassionally we find a really big one that requires a back hoe to remove. The biggest are just burried deeper, in a hole dug beside the rock. At this point they are half the size of a pick up truck and larger. Not many of those thankfully!!
The rocks in my part of the world were tansported here via a glacier from the North. Most are worn from the ride. I would love to find any of value, but as of yet not a thing....
Regards, Kirk