All of the stone for our house has come from our farm. Most of it was "free stone," which around here manifests itself as nice rectangular chunks. In other words, I picked it up from the ground, out of the creek, and from the hillsides where natural erosion and uprooted trees uncovered the layers that had been hidden for millions of years. One day late last summer, I decided to be more deliberate at my attempt to acquire some of this stone.
I began my experiment by choosing a neglected corner of a pasture where I thought I might like to have a small pond and where I was fairly certain that several layers of stone lay within 4 feet of the surface. Even though the grass barely grew in this location, I was careful to stockpile (with a backhoe) all of the top soil I could before digging into the subsoil. In case the pond didn't hold water, I could reclaim the hole by filling it up in reverse order... rubble, subsoil, then topsoil. After digging about 4 feet down, I hit a layer of stone which I carefully uncovered and swept with a broom. Most self-respecting pond diggers would utter a series of expletives upon discovering stratified rack at the bottom of their pit (it's a notoriously leaky foundation for ponds), but I was thrilled. My initial goal was to get as large of slabs as possible... since you can always make them smaller. I cut a rectangle in the stone with the Stihl chop saw, careful to note where the natural cracks in the stone bed already existed. Then with much anticipation, I pryed my first bit of stone free from the ground.
Cutting stone with the saw was noisy and dusty, and the exhaust from the saw lingered in the shallow pit with me when the breeze died down. At one point, I could feel the fumes or Carbon Monoxide getting to me, so I climbed from the pit for a breath of fresh air. As my mind cleared up, I remembered that local history is littered with stories of well diggers who suffocated from gas in the pits they were creating... and of more stories of the would-be-rescuers that succumbed in the pits as well. Whereas they had the innocent, if not ironic, misfortune of discovering natural gas, I was creating my own pollution and could do something about it. I made a mental note to run the saw as little as possible and to wait for a strong breeze. If my body decided to take a dirt nap in this pit, it would be midnight before anyone came looking for me. Although more labor intensive and less precise, using the spud bar to exploit natural cracks in the stone became my preferred method of liberating the stone.
Much to my disappointment, due to natural faults, most of the chunks were not coming out of the ground as large as I had hoped. I was really searching for large monolithic material that could be used for window sills and book shelves (rarely do you find it laying in this condition on the forest floor). But I had expended tremendous effort to create the hole in the ground, so I pressed on. I knew that I would be able to use this stone somewhere and I wanted to finish the experiment. If nothing else, these stones were unique (among those on our farm) for their thin yet consistent thickness. I could probably use them for stone flooring, if not inside the house, then at least for patios and walkways.
I manually wrestled quite a few stones from each of the layers until I reached the lowest layer. Beyond this last layer, I could find nothing of value. From there on down it was a mixture of hard-packed blue shale and clay. Useless for my building purposes, but harder than even the stone for the backhoe to dig through. I persisted through about 18 inches of this stuff, before I quit probing. Bummer... I had hoped to find more layers of stone to reward the work I had invested in removing the "overburden." At least this blue clay/shale makes a good pond liner.
With mixed feelings about the results of the experiment, I proceeded to remove the rest of the stone with the two foot bucket of the backhoe, wasting very little time to preserve large chunks. What I got from the final hasty backhoe process was rock less suited for flooring, but still usable in stone walls if faced or shaped with a chisel. In fact, the thin stones earned in this gamble have been proving very useful
in composing the dry-laid puzzle that forms my fireplace.
To summarize, my previous experience of unearthing thicker rock from a hillside was considerably more productive than this attempt at digging thin stones from a pit. I invested about ten hours of equipment time ($40/hr x 10hrs = $400) and two days of hard labor (priceless), for which I produced about six tons of usable stone, with a new watering hole for my livestock as a positive byproduct. No doubt a life enriching experience, but my first preference will always be to look for rocks that have been exposed by natural forces.