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Authentic Fossil Fern

Llewellyn Formation, St. Clair, PA.

Pennsylvanian Age 300 Million Years

St. Clair, Schuylkill County, PA is one of the few places where one can find these very detailed white (sometimes yellow) ferns on a striking contrast of black shale. The plants died and fell into the swamp, where in a low temperature, pressure, and oxygen environment the plant tissue was slowly replaced by pyrite (from sulphides). Pyrophyllite (aluminum silicate, a whitish mineral) is believed to have replaced the pyrite at a later stage as the sediments piled up and the temperature and pressure became greater. The ferns most commonly found are Alethopteris, Neuropteris, Pecopteris, and Sphenophyllum.