Shown below, are some Pennsylvania fern
fossil specimens from my collection
| Fossil ferns are very common in coal mining areas, the world over. It is the unique state of preservation of the white fossil on black shale, that gives the St. Clair, Pennsyvania fossil ferns their great beauty and rarity. Most fossil ferns are brownish black on white, gray, tan, or brown host rock. Nowhere else have ferns of such a pure white color been found! The ferns died about 250 million years ago (Pennsylvanian Period), and fell into a swamp, where in an anaerobic, low temperature, and low pressure environment, the plant tissue was slowly replaced by Pyrite (from Sulphides). Pyrophyllite (Aluminum Silicate) is believed to have replaced the Pyrite at a later stage, as the sediments piled up and the temperature and pressure became greater. It is the Pyrophyllite that gives the ferns their white color. The ferns most commonly found, are Alethopteris sp., Neuropteris sp., and Pecopteris sp. The Horsetail, (sphenophyllum sp.) is also relatively abundant. |
 Shown above, is a St. Clair fern fossil. It has the typical white fossil on black shale. Llewellyn Formation |
 Here is the big brother. It is 18 inches across. Notice the crossed fern leaf fronds. |
 This is a close-up view of the crossed fern leaf fronds. |
 This is the back side. Notice the rusty corners, indicating the presence of iron. |
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