Name:   Fossil Seed Ferns Age:  Pennsylvanian Formation:  Llewellyn Formation Location:  Near St. Clair, Pennsylvania Size:  Plate is over 10 inches across This is a very detailed plant fossil. It is a striking plate of fossil fern fronds from Pennsylvania. This specimen is replaced with the mineral Pyrophyllite, which gives the fossil its stunning color. Usually, the fossils are white - however, this layer produced fossils with a yellow tint. The long fern fronds have great detail and contrast beautifully with the black matrix plate. And there are two different types of ferns represented. This is a very displayable grouping of fossil fern fronds from the Coal Age.