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You can calculate the force needed to move it to get done sort of scale. Got to get the chemical mix right for predictable results. Someone I know used to get stuff from them when he worked in a slate mine. That was a big industry there, but not now.

We haven't been to Wales for years. It has a lot of industrial history for sure. We visited an coal mine that had been converted into a museum. Terrible working conditions for the miners back then.