panamark
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Member since September 2012
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Post by panamark on Oct 29, 2012 22:43:31 GMT -5
Okay, any geologists out there? Any idea what caused this fantastic formation? I found it on top of a bluff in western North Dakota and it is made of sandstone like material. Pretty soft and big - about 30" long. It does appear to have a couple fossil sea shells at the one end of it, so maybe it is some type of marine deposit. Obviously sedimentary, but why all the weird shapes? I don't think it could all be wind sculpting, could it? Anyway, I like it and hope y'all enjoy seeing it. - Mark
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keystonecops
freely admits to licking rocks
Member since October 2010
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Post by keystonecops on Oct 30, 2012 7:42:43 GMT -5
I'm with ya Mark. Dont have a clue but it is kewl. Later Clyde
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jamesp
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Member since October 2012
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Post by jamesp on Oct 30, 2012 8:07:40 GMT -5
What is that ? Should win Halloween scary rock contest.
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Deleted
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Post by Deleted on Oct 30, 2012 8:47:58 GMT -5
Looks like a couple of bush branches filled in when they rotted away. Chert nodules form in some very strange ways and a lot of them have a sandy outside like that but I have not seen anything quite like that. It is amazing that it has not broken which tells me that it must be some pretty tough stuff and not a soft sandstone. Jim
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itsandbits
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Post by itsandbits on Oct 30, 2012 9:13:49 GMT -5
I have a similar one from a different source I think because it is smoother on the outside; finer silt I think. I believe they are some kind of mudball conglomerate from strong silty river flows. I get them in my river but smaller also. I think if you were to find a broken one it is softer inside where it hasn't been altered. MY 2C
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Post by rockpickerforever on Oct 30, 2012 9:22:16 GMT -5
It is definitely a sandstone concretion. They come in various shapes and sizes. For photos and info on how they formed, Google "sandstone concretion formation". A lot of links to info there. Jean
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Deleted
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Post by Deleted on Oct 30, 2012 10:03:14 GMT -5
Thanks picker. Very educational. Jim
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firewalker45
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Post by firewalker45 on Oct 30, 2012 10:20:11 GMT -5
Looks like some Tampa Bay corral I have. You might want to cut one end to see if agate is inside. If there is , best cut in half length wise. Daniel
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billg22
spending too much on rocks
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Post by billg22 on Oct 30, 2012 13:38:19 GMT -5
It would look great in my garden.
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herchenx
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Post by herchenx on Oct 30, 2012 17:26:40 GMT -5
I found some similar - but smaller - formations in a clay bluff in Wyoming this summer. I broke them apart and they were 100% sandstone, but they would layer and break up in layers. There was one that had a big black crystal sticking out of it.
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Fossilman
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Member since January 2009
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Post by Fossilman on Oct 30, 2012 19:34:31 GMT -5
Its sandstone rock with rain and wind working on it.....See lots of that in the Musselshell Valley area in Montana...........(called sandstone concretion) Nice piece though....
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panamark
fully equipped rock polisher
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Post by panamark on Oct 30, 2012 21:11:14 GMT -5
Thanks for the link Rockpicker about concretions. Yes, this certainly seems to be a concretion. And the Wiki explanation even said it may be "extraterrestrial debris". LOL. I guess this really is a Halloween rock.
I was wondering when I found it, if it was some sort of entombment of a marine animal burrow. The reason I say this is because right nearby this piece was a big exposure of volcanic tuff (hardened once-airborn ash) that deposited about 20-70 million years ago.
The piece is uniform sandy material throughout the interior, so unfortunately the insides doesn't reveal anything. Why the sand+ash hardened in this particular shape is still a fine mystery to me. I guess the water just seeped into the ash+sand in this unusual manner.
I think it must be extraterrestial. Booo!
Thanks everyone for your input! - Mark
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rockingthenorth
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Member since January 2012
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Post by rockingthenorth on Oct 30, 2012 21:52:58 GMT -5
Thats cool...... I have found some but not that cool
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