Trio of Fossilized Ferns

Trio of fossilized fern specimens, two measuring 2 inches in length and the third measuring three inches. Source: St. Clair, Pennsylvania St. Clair fern fossils are estimated to be about 300 million years old from the Pennsylvanian Epoch of the caboniferous period. The matrix of these fern fossils is shale and the ferns often have a white coating which is known as Pyrophyllite, initially pyrite but was replaced during the oxidation process.