Coal balls, Coal Mining Geology, Kentucky Geological Survey, University ...
Definition and formation: Coal balls are calcareous masses of fossil peat found in coal beds. They are formed in the original peat before it undergoes coalification (DeMaris and others, 1983; Scott and others, 1996). Individual coal balls can be inches to many feet in diameter, and coalball clusters may occupy a small part (concentrated along the top or bottom) or the entire height of a seam.