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1153 Views 8 Replies Last post: Dec 31, 2014 12:33 AM by brettarcher RSS
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Mar 21, 2014 8:09 PM

Fossil Poo???

I am really hoping these are not just rocks. I've spent a lot of time gathering these recently and my collection has grown rather large. Please give me some good news lol! The one in my hand in the last pic weighs 28 grams. They are all very heavy for their size>>

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    Mar 21, 2014 10:26 PM (in response to Kristyx0x0)
    Re: Fossil Poo???

    Kristy,

     

    In general, the relaibility of coprolite ID depends on the presence of;

    - fragments of what was once food - plant or animal, sometimes pelleted

    - external shape - distinct turd characteristics

    - association with the pooer in time and place

    - chemical composition - perhaps phospatic

    For any one specimen, the more of those boxes that can be ticked, the greater the reliability of the ID.

    But many specimens are unclear on those points.

    And some of the unclear ones can be very difficult to distinguish from other things. There is real overlap in the classifiction: in some cases, pyrite/marcasite nodules may represent coprolites, for instance.

    With 'possible coprolites', one should try to ID them as other things. Some rusty-brown lumps turn out to be industrial waste; others fossil nuts. If you can't ID them as anything, they really be nothing of significance - just a lump of something.

     

    In your case:

    - I see no evidence of food remains, but I am going only on your photos

    - the external shape could be more convincing

    - I don't know about the time/place/association - were there fossil animals in the same rocks that might have been the poopetrators?

    - some of them look like 'just' marcasite nodules

    - I think coprolite is also possible for most of those; not the angular one.

     

    So...

    I suggest you crack one open to see if it has the usual marcasite structure (fine crystals radiating from a more-plain core).

    Be happy with marcasite nodules, assuming they are so.

    Learn to accept that it is not possible to ID everything, at least not without deeper research - which may require equipment, skills and knowledge beyond one's current means.

    By all means continue posting here - that's one way of accessing others' expertise and experience. It also gives responders, like me, a chance to see things we have never seen before.

     

    Mike

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      Mar 22, 2014 8:05 AM (in response to Kristyx0x0)
      Re: Fossil Poo???

      Kristy,

       

      Definitely marcasite nodules, and they may be coprolitic.

      For ref: http://www.ebay.com/gds/Marine-Reptile-Other-Coprolites-/10000000005960711/g.html

       

      Why you have so many scattered around, I can't say. I can say lucky you, though!

      Where I grew up, on the chalk of SE England, marcasite nodules occur in the chalk, but they are relatively rare.

       

      Some of yours are cracked open, so the once sparkly crystal interiors have weathered to rust. But the radial structure and massive core are still visible. If you break a fragment open, it could still be sparkly inside (as you have discovered) - it depends how long they have been weathering (and marcasite is less stable than its relative, pyrite).

       

      The holes you mention are where the cores have 'rotted' and fallen away.

       

      Fossil imprints, or indeed fossils, are possible. However, in those cases, the nodule might be a different iron mineral, such as limonite or siderite. Have a read of this on ironstones - http://en.wikipedia.org/wiki/Ironstone.

       

      Mike

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        Dec 31, 2014 12:33 AM (in response to MikeHardman)
        Re: Fossil Poo???

        i used to collect these from chalk  and beachy head has tons of them!  incertainplaces!  radiating structure are definitly pyrite or marcasite and beenexposed along time which accounts for the rust if they are not rusted through theywill shine likegold if freshlybroken however they will rust moreexposed to air esp if they are maracasite and change to limonite

        i havea nodule that was fresh in 80´s The centre is nowlimonite witha selenite growing too

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    Dec 18, 2014 6:08 AM (in response to Kristyx0x0)
    Re: Fossil Poo???

    Hello Kristyx0x0,

     

     

    Did you ever get any better answers on this question? Your pictures were the first of any I've seen like my own collection. The closest thing I could find to the ones that ARE NOT shiney and cystalike inside was a picture of titanium ore and a picture of geothite and hematite. At first I thought they were iron ore, but I kept looking because they didn't stick to a magnet, which iron should. You find out anything new?

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