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Lone Hunter

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Collected this a few years ago on the bank of Trinity river near the surface. There was a layer of sorts of this and that's where this concretion was containing a little Baculite poking out. So I'm assuming this is result of some evaporate process and this is gypsum but how did it come about? Was the concretion sitting in shallow muddy water? Hoping someone can explain the process that produced this.

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Interesting! 

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Mark.

 

Fossil hunting is easy -- they don't run away when you shoot at them!

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The primary ingredient in the formation of concretions is ground water, the solvent which mobilizes the elements. I suspect that this material dried and shrank in the first stage leaving a relative void around it which later geodized  when mineral crystals had room to grow.

Just my thoughts. Stay tuned for rebuttals. :)

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Sounds like a reasonable explanation, so strange it happened on a curved surface though.

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16 minutes ago, Lone Hunter said:

Sounds like a reasonable explanation, so strange it happened on a curved surface though.

Well, think of a septarian concretion that refused to crack. All the fill space would have a dome shape on the perimeter.

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Interesting; it looks like the (clayey) core of a concretion with an outer layer of gypsum, although we are not sure that the gypsum layer formed a complete envelope around the mud core (or have you seen some like that?). But the direction of growth of the crystals is towards the surface of the clay core, so the surface from which the crystals enucleated is missing. I have seen selenitic gypsum crystals growing on muddy layers triggered by bacterial activity, but that was in a cave environment.

ciao

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This is a steinkern partially covered with minerals that would make a pseudomorph of the shell if the process was complete. Sort of what Rockwood says. Aragonitic shell is dissolved and then gap is refilled with calcite.

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2 hours ago, Plax said:

This is a steinkern partially covered with minerals that would make a pseudomorph of the shell if the process was complete. Sort of what Rockwood says. Aragonitic shell is dissolved and then gap is refilled with calcite.

No beak is present in either picture of both sides.

~ Isaac; www.isaactfm.com 

 

"Don't move! He can't see us if we don't move!" - Alan Grant

 

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I don't see any evidence of it being anything but a concretion with a Baculite, shape is wrong for clam. The only similar mud crystals I've seen are at Yellowstone.

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It may not be what I've suggested but have seen what I'm suggesting many times. Might not be a clam steinkern but there was a gap filled with mineral crystals so we need to figure out what that space represented. I don't see a baculite but you have it in hand and can judge better than I.

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I can't see a baculite, either. The rest is a concretion, but I am unsure of what the void was.

~ Isaac; www.isaactfm.com 

 

"Don't move! He can't see us if we don't move!" - Alan Grant

 

Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry.

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Just wanted to mention this wasn't the only thing with these crystals, there was an area of several feet wide that had these, it was mostly flat though broken up and sitting on top of and connected to the dirt.

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plus, could you show the item by placing it on the surface with crystals? I wonder if the surface covered by the crystals was part of a larger (wavy?) one, or if it covered the central core at its present size. Since you have seen the original outcrop, which of the two hypotheses do you think is more reliable?

...Sorry, it's my language problem, but I can't get the exact meaning of what you're saying here: "(...) it was mostly flat though broken up and sitting on top of and connected to the dirt" Could you explain it differently? Thank you. Ciao.

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I'm not sure o understand, what do you want me to place on crystal surface?  If you mean the original surface at the river it is long gone,  I'll try to explain better what it looked like, imagine a frozen water puddle stepped on, it would break up into pieces and there would be dirt imbedded in bottom layer of ice which would no longer be level.  This was amongst all the broken layer of crystal, how large an area it was not sure because the erosion at edge of bank was breaking away and caving in and took some of the crystals with it.  As far as object circled in above picture it is the end of broken Baculite.

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On 8/8/2022 at 2:53 AM, Lone Hunter said:

Ah, ok, thank you,

…I mean if you can turn the object over and show the opposite surface

 

IMG_20220807_195208067.jpg

 

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Oh that surface :DOH: Here it is, some of the  crystals that came off covered the part outlined, I don't think it enveloped the whole thing.

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On 8/11/2022 at 12:40 PM, Lone Hunter said:

looking at this image it seems that the crystals covered the whole thing, since they grow at right angle on the edge of the "pebble"

 

IMG_20220811_050703768~2.jpg

 

Edited by supertramp
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Its entirely possible, can only imagine how cool that would have looked!  Would it have been inside a round void for that to have happened?

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