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743 Views 7 Replies Last post: Mar 20, 2014 9:40 PM by Tabfish RSS
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Mar 18, 2014 9:35 AM

They Look Like Fossilized Bones To Me, But I'm No Pro...

I'm new to fossil collecting so i could use some help with identification of these.  They look like they could be bones, but then again they could just be rocks.

  • Kristy,

     

    Yup - they're just rocks.

    Of course, the rocks comprise mineral grains and mineral cement, and some of the mineral grains might be tiny fossils.

     

    I know you're only just into fossils, but there's a lot to be seen with a hand lens. A good one somewhere in the range x10 to x20 could be an eye opener. (You might graduate to a microscope later on.)

    Here's what I mean: this one has both x10 and x20 lenses, protected in a metal case

    http://www.geosupplies.co.uk/proddetail.php?prod=ruperlensx10x20

    When a hand lens lives in your pocket, especially while you're doing field work, it is important to protect the lenses from grit and knocks. Such a metal case does the trick.

    If you Google 'geological hand lens', you'll get lots more hits.

    Just a thought...

     

    Mike

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      • Kristy,

         

        That's a powerful lens!

        The usefulness of a lens depends on several factors, not just magnifying power. Spherical and chromatic aberration are serious problems on many lenses, especially higher-powered ones. I hope, and expect, your jeweller's lens is of good enough quality that it is not affected much in that respect.

         

        What you might be looking for depends on the specimen and the particular question needing to be answered.

        With many fine-grained and homogenous rocks, it is not obvious whether they are sedimentary, igneous, or metamorphic. With a good hand lens, you may be able to see details that help resolve that important distinction. If you see rounded grains with a cement holding them together, that would a suggest sedimentary rock. If all the grains were angular and interlocking, that would suggest igneous or metamorphic. Also, you might be able to see microfossils, which would be a good indicator of sedimentary rock. (Metamorphic rocks are always going to be a bit more tricky, since they arise from any type of rock and since rocks affected by very low-grade metamorphism are little different from the original. There is also a process called diagensis, which covers what happens in the process of sediment becoming rock - and that can involve processes with similar effects to metamorphism (such as pressure solution).

        That's all general stuff. I encourage you just to look at all sorts of rocks using your lens. You never know what you'll see, and what will strike you as interesting.

         

        As regards (vertebrate) bones and teeth (and lets include woody plant material): they have cellular structure, which can be small enough that you would need a lens to see it (especially with bones of small creatures). There are photos here of the structure of bone, at various magnifications (don't expect to see things like the high-mag images by using your hand lens) - http://depts.washington.edu/bonebio/ASBMRed/structure.html. Those photos show modern bone. With fossil bones, the cavities would be filled with mineral, so they would not be quite as obvious. With teeth and tusks, there are somewhat different structures. And wood is different again, especially since in includes larger-scale structures such as medullar rays.

         

        Lastly, just because you see a cellular structure, it doesn't mean it is bone/tooth/plant. There are many invertebrates whose exoskeleton shows a cellular structure, such as some bryozoans. Here's an example (from http://www.nps.gov/grca/naturescience/fossils.htm).

         

        Mike

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      • Hello Kristy, interesting finds.

        You have an eye for different rocks so keep looking and showing us what you find.

         

        Tabfish

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