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OT - Metal? Mysterium? Cannonball?

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  • #16
    Bobl has it right. It's a pyrite nodule common in Tx. They form in the limestone that is the underneath most of the state. Before we were a Republic ,we were an inland sea!

    Tim in D

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    • #17
      "2. Heavy, like Lead or dense Cast Iron."

      what is dense cast iron?

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      • #18
        Originally posted by MickeyD
        That looks a lot like a chunk of river tumbled low grade iron ore. We had a lot at the farm when I was growing up and smaller chunks were great in slingshots.
        I would agree with Mickey
        Haematite (kidney ore) exhibits that crystalline appearance
        http://www.irocks.com/db_pics/greenbank/lg06a.jpg
        The fractured back of this sample would exhibit the crystalline structure you see. I think your sample is just heavily corroded

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        • #19
          Was pyrite, is now hematite/goethite

          BobL is spot on with his description:

          "" . . a weathered pyrite (or marcasite) nodule. The mineral was originally iron disulphide.
          I can tell from the way the original crystals radiate out from the center of the nodule (right hand image)."

          I pick these things up around Austin, TX from time to time. The ones I have collected are definitely pyrite (as opposed to marcasite) confirmed by powder x-ray diffraction. The nodules typically have a granular center and then crystals radiating outward. They originally formed under low-oxygen conditions. Once exposed on the surface, the pyrite (iron sulfide) turns into either hematite (iron oxide) or goethite (iron oxide-hydroxide) or limonite (iron oxide hydroxide hydrate).

          We home shop machinists should know goethite when we see it--it is naturally occurring rust :-)

          --Weekend
          My cup 'o plasma: https://www.youtube.com/watch?v=H1vMfmhM9fg No dialog, just ten minutes of dancing plasma and music. Turn on, tune in, space out.

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          • #20
            We, as kids would find them in soft shale in creek beds. We erroneously called them, "fools gold". If you break it open, it is quite pretty inside.

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            • #21
              Magnets

              On the issue of "does it stick to a magnet"

              Do you want to know if something interacts with a magnet, even very weakly? Try this:

              Get about a one inch diameter neodymium iron boron magnet and suspend it from a piece of thread. If possible, the thread should be a foot or more long. Mount the thread to a fixed object like a shelf over your workbench. This will give you something of a pendulum with the magnet as the bob and very little force will be needed to deflect the magnet.

              Then bring the object under test near the magnet. If the mystery object even weakly interacts with the magnet it will noticeably deflect the magnet.

              If the magnet doesn't settle down fast enough for your liking, put a large aluminum or copper plate below but not touching the magnet. This will dampen the swinging (eddy current breaking) but will not attenuate the interaction of the magnet with the mystery object.

              Obvious disclaimer: Don't bring a large iron object near your "magnetic pendulum" You will instantly break the thread as the magnet goes screaming toward the iron. You'll probably end up breaking the magnet too.

              --Weekend
              My cup 'o plasma: https://www.youtube.com/watch?v=H1vMfmhM9fg No dialog, just ten minutes of dancing plasma and music. Turn on, tune in, space out.

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              • #22
                Petrified dianosaur turd!!!!!

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                • #23
                  I havent a clue what it is but what i'm looking at is the distinct presence of solidification patterns, it was liquid, and cooled from the outside inward, the dendritic aka columnar features always follow the directiom of the temperature gradient, cooling was very fast, more than 50% of the shell is dendritic, this formed the crust,in the central portion the remainder of the mass seems to show that cooling was slower and equiaxed crystals have formed.
                  the 'rays' are inward not outward, judging by this a water quench was involved,like ingot casting
                  http://www.substech.com/dokuwiki/lib..._structure.jpg
                  mark

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