This specimen is a cast of the outside bark pattern of the midsection of the Sigillaria tree. The corrugated pattern runs vertically with the trunk orientation. Note the thin layer of coal covering the surface-- the remains of the woody tissue of the tree. This layer is about 1/16 inch thick -- representing the total thickness of the tree after dewatering, compaction, and coalification. If you look closely you will see little bumps in the furrows. A leaflet was attached at each one in life.
Rock Type: Gray sandy shale
Interval: 5-Block (Lower Kittanning) seam
Age: Middle Pennsylvanian Period, approx. 304 million years.
Location: Nicholas County, West Virginia; Spirit Ridge Surface Mine #1, operated by Peerless Eagle Coal Company, located about 8 miles northwest of Summersville, West Virginia. Follow Route 39 west from Summersville to Gilboa about 5 miles. Turn north onto Hutchison Branch Road 1 mile to guardhouse. Collecting is on top of ridge overlooking Twentymile Creek.