Coal Balls: Preservers of Organisms That Lived in Ancient Swamps (CO-04)
Coal is the product of altered plant debris that accumulated in vast swamps during the Pennsylvanian Period more than 240 million years ago. Odd rounded rock masses of calcite and pyrite are common in coal seams in southwestern Indiana. These coal balls, whose long axes range from 1 inch to as much as 3 or 4 feet, are useful to scientists who seek information about the origin of coal - Indiana's most important energy source.

The intricate preservation of both plant, and less commonly, invertebrate animal fossils or insects has intrigued several generations of geologists and paleo-botanists. Coal balls have enabled scientists to learn more about organisms that lived in ancient swamps. Comparison of coal-ball material and samples of modern peat has shown significant differences in the plant groups but very small differences in the peat-forming process.

Our Hoosier State Beneath Us: Coal