File:Coal ball (Duquesne Coal, Upper Pennsylvanian; Steubenville West roadcut, Ohio, USA) 1.jpg

English: Coal ball from the Pennsylvanian of Ohio, USA. (~6.5 centimeters across at its widest)

"Coal balls" are fossiliferous limestone nodules that occur in some coal beds. They contain three dimensionally-preserved plant fossils, which are significant for paleobotanical studies. This example comes from a sub-bituminous coal horizon in eastern Ohio called the Duquesne Coal (pronounced "Doo-kane").

Coal ball fossils can be examined using thin sections or acetate peels. The latter involve cutting and polishing a coal ball, etching the surface with hydrochloric acid, adding a thin film of acetone, and rolling a piece of acetate paper onto the surface. When dry, the acetate paper is peeled off and placed under a microscope to see cellular-level details of the fossils. The treated acetate paper can be put between two pieces of glass and taped together.

Stratigraphy: Duquesne Coal, lower Casselman Formation, middle Conemaugh Group, Missourian Series, lower Upper Pennsylvanian

Locality: Steubenville West outcrop - roadcut on the southern side of Route 22, just east of Reeds Mills Junction, west of Steubenville, eastern Ohio, USA (40º 21' 46.89" North latitude, 80º 45' 45.65" West longitude)