Carbonate petrology and geochemistry of Pennsylvanian coal balls from ...
1. Introduction. Over 100 years have passed since Stopes and Watson (1909) proposed a marine origin for coal balls, which are carbonate concretions that formed in peat and contain anatomically preserved plant material. Most coal balls occur in paleotropical coals of Pennsylvanian and early Permian age. Although calcium carbonate is the primary mineral, coal balls usually contain pyrite ...