Modern analogs reveal the origin of Carboniferous coal balls
Introduction. Coal balls were best defined by Seward (1895, p. 85). "In the Coal Measures of England, especially in the neighbourhood of Halifax in Yorkshire, and in South Lancashire, the seams of coal occasionally contain calcareous nodules varying in size from a nut to a man's head, and consisting of about 70% of carbonate of calcium and magnesium, and 30% oxide of iron, sulphide of iron, etc.