2) A regional form of shale.
The search for coal obliged miners to sink shafts and drive passages through earth, rock and a variety of minerals which they considered to be of little or no value, and all this waste matter had to be taken out of the pit and stacked or distributed on ground close to the pit-head. It is in such contexts that we find the word ‘scale’. In 1665, two Bradford men were ordered at the manor court to remove all the gravel of earth and scale digged forth of the … Cole Pitts, which by their procurement was throwne into the high wayes and ditches belonging to Heaton. In 1777, the lessees of a pit in Southowram were granted room where they might store the coal and also all such gravel, Stone, Scale and Rubbish as shall arise in Sinking of the same pitts
spoil heaps that is.