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elephant ears of bluestone
Friday, November 1 2013
I'd cleared all the shale and weak layers of bluestone off a bench of much harder stuff, but even in this hard stuff there were some cracks evident when viewed from the fault to the east. Using a cold chisel, I applied kinetic energy into some of these cracks, and successfully cracked loose a large irregular piece of the hard bluestone. It was so large that it lay at the very limits of my ability to move it in one piece. It was too heavy to lift off the ground (suggesting it weighed something like 300 pounds), but I was able to tip it end-over-end. Some of its edges were menacingly sharp, so I put on some gloves and put down some particleboard to protect the deck. Surprising even myself, I managed to get it out the door, up the steps, and then a few feet out away from the greenhouse.
I managed to remove several such pieces, which, due to their size and shape, I mentally referred to as "elephant ears" (a term I also informally use for large plant leaves). These were all a bit smaller than that first monster, and some were light enough to be lifted. Unlike the kind of bluestone that is mined for pavers and other purposes, this stuff always broke irregularly, with thicknesses ranging from blade-thin to ridges and prominences several inches thick. Even so, these pieces tended to be more stackable than most of the loose bluestone that litters the nearby woods, and I used some of them to further augment a stone retaining wall running in an L-shape between the greenhouse and the brownhouse. This retaining wall hasn't actually been retaining much, as there hadn't been much fill dumped uphill from it. Now, of course, I've backfilled behind that wall with an enormous amount of broken shale. But it seems most of the rock I'll be removing from now on will be in the form of large elephant ears of bluestone.
As I wrestled the large unweildy pieces of bluestone out of the greenhouse, I found I could safely lift and move larger pieces if I always remembered to wear the gloves, which rendered the sharpness of the fresh new edges completley irrelevant. (Generally I don't like to wear gloves when working with my hands; I find they blunt my ability to "feel" what is going on, but sometimes they're very helpful.)
One of the interesting things I've noticed about breaking up bluestone bedrock is that when it can finally be coaxed into cracking and separating, those cracks come in one of three forms. Some of the cracks are full of mud, suggesting that they were existing voids in the rock gradually filled in with sediment. Some of the cracks are merely moist, suggesting that they were only large enough to admit water. And then there are cracks that absolutely dry, even in rocks that have been soaking in water. This suggests that the crack did not exist at all until I stressed the rock to its breaking point.
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