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dpreynolds

Iron balls (?) found at seashell fossil level

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dpreynolds

Although I am brand new here, I already have a question. Unfortunately, no photos yet, but I will describe the best I can.

I see these things at Lake Pueblo on a regular basis. In the light grey sediment/shale, where i find seashell fossils, I also see small balls (3/4" or so) that look like iron. They have a color like rusted iron. Rough on the outside. Almost perfectly spherical. They discolor the rock that holds it (slightly) around the ball. I have not checked for magnetic characteristics. I cut one open and it seems to have a starburst type pattern on the inside. I heard somewhere that when hot metal (iron) is cooled quickly (possibly when this area was a sea), it may leave that pattern. I also wondered if they are round because they were molten and hit the water, cooled quickly, and sank to the bottom, to the sediment. Does anyone have a general idea of what they may be? I have my uneducated theories...So, if anyone can shed light, it's been driving me nuts. Thanks!

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Rockwood

Iron rich concretion.

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fossilnut

@caldiggerWhat an aggregation of Moqui marbles! I thought you might find one here and there but not in this abundance. Is this common? Where is this general area where the picture was taken?

@dpreynoldsWhat you describe as a star burst pattern I believe I have seen in marcasite nodules. Usually a hole at the center and the pattern I believe are crystalline marcasite. Others will know more. Welcome to the forum a lot of people with more knowledge than me.

Screenshot_2020-01-17 marcasite nodule - AOL Image Search Results.png

Edited by fossilnut
added welcome and picture

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fossilnut

Does not look like picture came through. Will try again Cockscomb marcasite

DSCN6051.JPG

Edited by fossilnut
got picture to show

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dpreynolds

 @caldigger that photo looks pretty much exact except for the one that's broken. The inside is different. I haven't found any grouped like that. Just singles in the shape. 

I'll be back down there and get photos and post them, probably sunday.

 

So what creates them at the level of the shells? 

Also, thanks @fossilnut and @Rockwood!

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caldigger

That picture is from a deposit in Utah.

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Mark Kmiecik
2 hours ago, dpreynolds said:

 @caldigger that photo looks pretty much exact except for the one that's broken. The inside is different. I haven't found any grouped like that. Just singles in the shape. 

I'll be back down there and get photos and post them, probably sunday.

 

So what creates them at the level of the shells? 

Also, thanks @fossilnut and @Rockwood!

Google Moqui Marbles -- there's a ton of photos and info online. Some locations in Utah have DRAMATIC amounts in a small area. There's some info on how they formed also. The size seems to range from pea to baseball.

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Rockwood

Ping pong ball sized examples are fairly common in Maine.

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grandpa

Sounds a lot like the pyrite/marcasite/limonite nodules found in cretaceous fossiliferous  limestone formations in Austin, Tx.  Of course this is a guess based on no photo references.

 

And, oh yes, if I haven't said so earlier, welcome to TFF from Austin.

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