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428 Views 3 Replies Last post: Jul 3, 2013 9:33 PM by MikeHardman RSS
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Jul 1, 2013 10:15 PM

Unidentified bone? Or perhaps not.

Hi I was out this evening on a local coal batch in Somerset sifting through some of the brittle slate-like rock when I came across what looks like a bone (see pictures below). I know that coal was produced circa 300 million years ago in the Carboniferous period, but does anyone know what this might be? Thanks. Mark

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    Jul 3, 2013 2:14 PM (in response to MarkO)
    Re: Unidentified bone? Or perhaps not.

    Hi MarkO,

    Not sure from the photographs. Please can you confirm that the specimen is grey and similar texture throughout? Does it look like the country rock?

     

    It is difficult to tell from the images, but the features you see may be as a result of brittle fracture.

     

    Rocks can break in fascinating forms due to structural pressures created during the history of the rock. Another type of structure that you may come across is "plumrose structures", you can see what these look like if you google

    http://www.earthscienceworld.org/images plumrose structures

    Plumrose They record fracture propogation direction in rocks. Feather-like structures which form under extensional rock forces during a rapid pulling apart of the rock.

     

    I look forward to hearing what you think.

     

    All the best,

    Fiona

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      Re: Unidentified bone? Or perhaps not.

      I think you mean 'plumose' .  Plumrose sounds like a tasty fruit bearing plant

       

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        Jul 3, 2013 9:33 PM (in response to quagga)
        Re: Unidentified bone? Or perhaps not.

        Yes - plumose not plumrose; methinks Fiona's spellchecker might be to blame.

         

        I don't think there's a fossil here; the subject looks to be of the same composition as the remaining rock (which is indeed rather slaty). That can happen where the fossil is a cast, but I don't see that here.

         

        I think is it just a quirk of the natural fracturing of the rock. Rocks have various sorts of fractures - joints, cleavage surfaces, faults, tension gashes, etc. Although they may form at somewhat different stages in a rock's history, they can interfere and intersect, producing suspiciously-symmetrical or otherwise-interesting shapes from time to time.

         

        Mike

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