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386 Views 4 Replies Last post: Oct 18, 2013 4:45 PM by Dan RSS
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Oct 11, 2013 6:57 PM

How do you tell if something is fossilised

I Have been finding some objects, but I don't know if they are modern or fossilised.  Would it work if I put them in boiling water so if they aren't fossilized they will go soft- or would it damage them if they are fossilised?  I just want some tips really.

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    Oct 12, 2013 3:19 PM (in response to Dan)
    Re: How do you tell if something is fossilised

    Dan,

     

    Please read my last post (2jun13) here - http://www.nhm.ac.uk/natureplus/message/29550#29550

     

    Even real fossils can be damaged by putting them in boiling water, or even cold water - it all depends how fragile they are; the most fragile ones will be reliant on the rock for support, and that can crumble in water. But in simplistic terms, boiling a real fossil will not make it disintegrate, though the heat could make it break into smaller pieces. If they go soft, they would be unlikely to be fossils.

     

    But you can also go on density. Most fossils, being made of rock/mineral, will be denser than water. There are exceptions, such as insects in amber, and fossils containing a sealed cavity.

     

    If you find a specimen still in place (in situ) in the rock, that must be a fossil. But even here, the rule does not always hold, because with friable sediments it can be difficult to say if it is rock or modern sediment (soil/alluvium/etc.)

     

    If it is a specimen you can ID and it is known to be extinct - fossil (or maybe subfossil if recently extinct)

    Otherwise:

    - If it is in situ in rock - fossil

    - If it is in situ in rock or modern sediment - fossil / subfossil / non-fossil

    - If it is ex situ (eg. loose on a beach), and floats on water - probably not a fossil

    - If it is ex situ (eg. loose on a beach), and sinks in water - fossil

     

    Mike

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