Seatearth is a British coal mining term, which is used in the geological literature. As noted by Jackson, a seatearth is the layer of sedimentary rock underlying a coal seam. Seatearths have also been called seat earth, "seat rock", or "seat stone" in the geologic literature. Depending on its physical characteristics, a number of different names, such as underclay, fireclay, flint clay, and ganister can be applied to a specific seatearth.