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I've always wondered what this is...

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This thing has been a lifelong mystery to me.  I'm finally reaching out to the experts here to find out what it's real story might be.  

My dad was a navy man, visited every continent but Antarctica.  Somewhere, sometime before I was born, he found this rock "laying on the beach" (I don't know what beach, what ocean, or what continent).  It sat on a his bookshelf every day of my life and it was endlessly fascinating to me as a kid.  I always immagined it to be a metiorite, crashed to earth on some exotic ocean shore just before my dad reached down to pick it up!  My dad recently passed away and I brought it home to put on my own bookshelf and I'd sure love to know what it really is.

I guess the photos will be the best description.  There are two facts that the photos don't really show.  First, it's heavy (seems noticably heavier than a rock this size should be).  Also, the surface is completely covered with these "spikes" that are worn flat at the ends and every one of those worn spots look very much like rusted iron, not grey-brown like the rest of the surface.

Any ideas would be greatly appreciated!









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Hello Turtlerock,  looks like a very weathered iron concretion of some sort.  It may be natural, or it may be man made.  Maybe a solid shot cannonball, or a round iron weight for automatically shutting a gate.

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Thanks 4meter.  That is SO intriguing!  I'm pretty sure that my childhood self would have thought that the possibility of it being an ancient cannon ball was even cooler than a meteorite.

It's always looked iron-ish to me but I never thought to test it until after reading your comment.  I don't have any sophisticated testing equipment but I treid a couple of ideas.  I checked to see if a strong rare earth magnet would stick to it and... nope.  But I did find that if I passed it very close to a good orienteering compass, without touching it, it deflects the needle ever so slightly.  Not sure what that proves, but there is something slightly magnetic about it.



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I was wondering what might be inside it.  I’m by no means an expert, but I wonder if that could be some sort of geode inside.  Those are nothing more than a gas bubble in a rock that over the eons minerals fill it up and then the outside rock erodes away leaving nothing but the geode that formed inside the gas bubble.  Sometimes these geodes are hollow and have interesting looking minerals inside them.  There are some geodes where I live, but especially compared to the amethyst geodes, the ones close to me are a boring brown like quartz with no hollows.

One of the pictures makes it look as if its been cut in half already and glued back together.  Only way to really tell is to whack it open or cut it open and look inside.  Done right though, cut in half it could still be used as something decorative and still have memory or conversation value like fixing it to a bookend or some other display.

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Thanks everyone for all of the info and comments!  
I tried the streak test and my first impression was that it was not making any mark at all. I was starting to wonder if it was too hard for the tile to abrade or something.  When I then filed a spot with a diamond file I realized what the problem had been; the dust that was coming off was about the same color as the tile itself, white to a very light grey, so it just wasn't showing up on the white tile.  Not sure what that result tells us.  Also, if you moisten the spot that was filed it goes back to being black/brown but the dust that the file produces is very light colored.
I looked up septarian nodules and that does seem most likely to be what it is.  There is one question I would have about that.  It's hard to tell from the first photos I posted but when you hold this thing in your hand, the first thing you notice is how "spiky" it's surface is.  It's covered with projections that feel like they were once taller sharp points but have been worn down.  The septarian nodules I can find pictures of often have the cool geometric divisions on the surface that are also very textured but I don't see any with this densely spiky character.  Have any of you ever seen that before?
Thanks again
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It's a large petrified coronavirus.:rolleyes:

Just kidding of course. I don't think it's a septarian nodule. While I see some similarities, I see some dissimilarities as well. I think the only way you'll ever know for sure is to cut it open, then polish both sides IF you like what you see. I would NOT use a hammer in it since you'll most likely destroy it.

You could leave it as is but like I stated, you'll never know for sure what it is.



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Morlock:  Haha!  Petrified covid; that'd be just my luck, taking all these precautions out in public and then sitting around the house with the mother-of-all covids on my bookshelf!  Wouldn't surprise me at all...
Chrisski:  It gives the impression of being re-assembled because of my poor quality photographs.  Seen in more detail, it has tiny fissures in the surface that look like the ones in a septarian nodule.
Here's a slightly better photo.


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septarain nodule, not.  It is a nodule,   Think marsian  “blue berries” found by the mars rovers, also found in places on Earth.  This is a big one.

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4 hours ago, 4meter said:

septarain nodule, not.  It is a nodule,   Think marsian  “blue berries” found by the mars rovers, also found in places on Earth.  This is a big one.

I don't think its a hematite concretion. Like a Moqui marble or a Martian blueberry. Hematite/sandstone spheres are common and get as big as dump trucks. But that's not one. 

I'll bet you a little gold nugget that is a septarian nodule. And I'd bet another it's not a sandstone/hematite sphere either.

Just my two cents. I could be wrong. 


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