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564 Views 3 Replies Last post: Mar 4, 2013 10:17 PM by MikeHardman RSS
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Mar 4, 2013 7:47 PM

Help me identify my son's rock find please

My 6 year old son found this whilst looking for fossils, bless him.  Is it a meteorite? or is that wishfull thinking.  ThanksP1010528.JPG

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    Mar 4, 2013 9:29 PM (in response to Tankaroonies)
    Re: Help me identify my son's rock find please

    To me, it looks more like tar than a meteorite.

    But it is a very reasonable question for a six year old to ask!

     

    Perhaps you could tell us more about it:

    - where it was found (place and situation)

    - density (does it feel heavy or light for its size)

    - odour

    - stickiness on the fingers, or not

    - hardness (when you hit it with a hammer, does it break or not, or dent; can you mark it with a knife)

    - magnetic (is iron attracted to it, is a magnet attracted to it)

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        Mar 4, 2013 10:17 PM (in response to Tankaroonies)
        Re: Help me identify my son's rock find please

        Tommy,

         

        Jolly good.

         

        I might add that, although one tends to think of tar as man-made, it can occur naturally as:

        - a consequence of oil (especially thick oil) exuding into the sea and eventually getting washed ashore

        - layered deposits, seeping or not depending on its viscosity.

        And when one finds tar balls on the beach, they may have come from ships, oil spills or natural seeps - it would not be obvious which.

        In a similar way, lumps of concrete (especially old, say Roman, concrete) can be mistaken for rock.

        So it is entirely reasonable for a rock hound, upon seeing what appears to be a lump of tar, to pick it up for inspection. No shame in that.

         

        Also, tar is an interesting substance in terms of its material properties (rheology, in relation to rocks). One can learn about geological deformation processes from studying it. Pitch (related to tar) is a rare substance in that its viscosity varies greatly with strain rate. That is: if you leave a piece of pitch alone at room temperature, it will slowly flow under its own weight (low strain rate), but it you hit it with a hammer (high strain rate) it will shatter.

        This experiment with pitch has been running 85 years so far - http://www.geekosystem.com/watch-tar-drip/

        So, again, no shame in a geologist being interested in a lowly piece of tar!

         

        I'm glad you think your son is hooked.

        Many people look, fewer people see, fewer still wonder and question.

         

        Regards,

        Mike

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