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1018 Views 7 Replies Last post: Mar 21, 2014 8:19 PM by Kristyx0x0 RSS
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Mar 3, 2014 11:37 PM

Rock, Fossil, Metal Orrrrr?????

found these while collecting fossils by my house in Fort Worth Texas. They were buried along with the fossils and are fairly heavy for their size. Hoping someone can identify them for me Because there are more where those came from and I would like to know if collecting them would be worth my time. I have also included a pic of the common Fossils I find in that same area for comparison. Any info on those would be appreciated as well, I am a beginner. Thanks For your time guys have a great day

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    Mar 4, 2014 9:08 AM (in response to Kristyx0x0)
    Re: Rock, Fossil, Metal Orrrrr?????

    Kristy,

     

    I think these could be coprolites.

    Calcium phosphate is assocaited with coprolites, and they can also be pyritized.

    Regarding their being 'fairly heavy for their size', high density could be due to:

    - if only slightly 'heavy': calcium phospate (density 3.14g/ml vs. 2.71 for caclcium carbonate)

    - considerably 'heavy': pyrite (~4.9g/ml)

     

    Pyrite can occur as nodules, unrelated to poo. But such lumps can look rather similar.

    The situation is confused further by pyrite specimens being more saleable/valuable if they are stated to be pyrite coprolites rather than pyrite nodules (I don't know why). Be aware of that when Googling 'pyrite coprolites'.

     

    In most cases, we cannot determine what creature made a coprolite (the 'poopetrator'!).

     

     

    You have a very nice assemblage in the 'associated fossils' (IMG_20140303_134058.jpg)

    top - ammonite

    top-left - oyster (possibly Gryphaea)

    left - maybe brachiopod

    bottom-middle-left - sea snail (gastopod)

    bottom-middle-right - sea snail (gastropod, spirals largely still in stone)

    right - bivalve or brachiopod

    upper-right - can't tell - need more and closer photos

    centre - sea urchin (echinoid)

     

    Mike

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