val james's picture


Observed: 1st December 2010 By: val james

i am curious to know if anyone can identify this stone for me it looks like some kind of fossil and was found in woodland.

  • fossil
    Confidence: It might be this.
  • Concretionary nodule
    Confidence: It's likely to be this, but I can't be certain.
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Peter Skelton's picture

probable pseudofossil - concretionary nodule

A curious-looking object, indeed! However, I suspect that it's a concretionary ironstone nodule, not a real fossil: the term 'pseudofossil' refers to something that looks like a fossil, but isn't. Such nodules form within sediments, due to the precipitation of minerals from groundwater in the pore spaces between the sediment grains (similar to the way 'fur' grows in your kettle, or in your central heating pipes). The precipitation process kicks off around some enticing nucleus - maybe a bit of organic material - and then builds out from that in concentric layers, hence the concentric banding that one can just about make out in your photo. In this case, the mineral was probably iron carbonate (called 'siderite'), which, on weathering, hence oxidation, imparts the red colour we see here. Siderite nodules are relatively common in silty mudrocks and fine-grained sandstones like that shown here. Sorry to disappoint, then, but thanks for posting it: it's useful to see such a nice example of one of the many kinds of pseudofossil that can waylay the fossil hunter! One final tip, though: with all photos of such things, as well as fossils, it's a good idea to include a scale (e.g. a ruler to one side) to give a guide to its size. In this case, for example, I can't really tell whether it's a few mm, or cm, or even a metre across.
Thanks, Peter

jhn7's picture


What an interesting find and thank you Peter for your clear explanation and identification.

Certificate in Contemporary Science (Open)

Lucy Corrander's picture

Pseudo Fossil

I'm glad I added this posting to my favourites because it drew me back to the Peter's explanation. I live in an area where there are lots of fossils (and nodules too) so I found it of special interest. Thank you.


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