The layer of paleosol, usually consisting of claystone or sandstone, that forms the floor of a coal seam. Because it represents the ancient soil that supported the peat swamp, it is typically depleted of alkalis and rich in alumina, making it highly refractory. Miners often exploit these layers separately as fireclay for manufacturing heat-resistant bricks.
Heard on the job
We need to leave a few inches of bottom coal to avoid tearing into the soft seatearth and bogging down the shuttle car.
Also heard as
- seat earth
- spavin
- thill