The Mather Sandstone Lentil (formerly termed Waynesburg) of the lower part of the Waynesburg Formation, Dunkard Group (Pennsylvanian and Permian), has been considered to be a more or less continuous deposit extending entirely across the Dunkard basin. The Mather Sandstone Lentil is restricted in areal extent to southwestern Pennsylvania and northern West Virginia. A similar sandstone deposit, which is present in parts of Washington, Athens and Meigs Counties, Ohio, and adjacent West Virginia has been considered to be a part of the Mather (Waynesburg) Sandstone. In the opinion of the writers these sandstones are homotaxial units; that is, they have a similar order of arrangement in different locations but are not necessarily contemporaneous. The sandstone of southeastern O io is herein termed the Hockingport Sandstone Lentil, from the village of that name in Athens County. The sandstone of southwestern Pennsylvania and northern West Virginia is herein termed the Mather Sandstone Lentil. It is suggested that both sandstone bodies are lentils of the Dunkard Group.

The sandstones are subgraywackes. The Mather Sandstone Lentil is locally conglomeratic and contains approximately 68 percent quartz. The Hockingport Sandstone Lentil contains much pebble and granule conglomerate and averages 61 percent quartz.

Both sandstones are elongate, belt-type deposits of fluvial origin. The Mather Sandstone Lentil has a thickness up to 75 ft (23 m), a preserved length of approximately 45 mi (72 km), and ranges in width from about 11 to 20 mi (18 to 32 km). The preserved deposit essentially blankets an area of 880 sq mi (2,279 sq km). The longer axis is oriented N20°E and the vector mean of dip directions of cross-stratification is oriented N5°E.

The Hockingport Sandstone Lentil attains a thickness of 100 ft (30 m) and ranges between 5 and 11 mi (8 and 18 km) in width. The length of preserved outcrop of the deposit is 28 mi (45 km), and its extent is approximately 225 sq mi (583 sq km). The longer axis is oriented north-south and the vector mean of dip directions of cross-stratification is oriented N8°W.