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Common Pseudofossils

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About Pseudofossils
Typical pseudofossils

Some of the variety of pseudofossils

Geology Expert photos
Sorting out fossils from other things was one of the first achievements in geology (in 1669). It's still a problem that puzzles regular people, who often send me pictures of odd things preserved within rocks. Fossils are signs of once-living things. Pseudofossils are something between organic (like a life form) and geometric (like a mineral crystal), but they owe their shapes to chemical and physical processes alone.

There are a few clues that help in telling fossils from pseudofossils. Fossils need special conditions to be preserved, and that's why they're typically found in well-bedded sedimentary rocks made of fine-grained mud, looking like leaves pressed in the pages of a book. Objects in other types of rock usually aren't real fossils. Fossils have what I can only call an air of purpose: a shark's tooth clearly has its shape to perform a function. Even coprolites, fossilized feces, are that way. Pseudofossils fail that test either by being too well organized, like a crystal or a blank spheroid, or too unorganized. See how those clues apply to the set of common pseudofossils in this gallery.

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