Years ago when I was a professional archeologist it was common practice to use a one or two man portable post hole auger to make a quick and dirty “posthole survey” of a likely site by drilling a series of closely-spaced holes and counting the number of artifacts that came out of each hole, thus establishing the extent and shape of the site. The holes with the most debitage, potshards etc was assumed to be the center of the site and would be investigated further. As Relevantchair points out, when the auger struck a large underground rock the auger stopped turning and the operator received a rather severe jolt and was sometimes thrown to the ground. Artifacts sometimes came out of the ground in pieces, but in archaeology, where the goal was knowledge rather than the acquisition of perfect specimens, this was often considered to be a justifiable sacrifice, especially if the property developer who was paying the bills didn’t want to pay for an extra week’s work for the sake of an intact arrowhead which he wouldn’t get to keep anyway.