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"Septarian coral"? From Morocco


sdsnl

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you have other samples too? can you put other pictures too? also some very close up images. these samples are very interesting. we should find what might be :|

I agree; this puzzle needs to be solved! :)

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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My thought is that the “regular” and geometrical shape is due to the fact that these nodules were actually part of a greater and fractured septarian-like one, with the convex facets being the fractures among one piece and the other…something like that (though this is not agate).

ciao

post-20300-0-64367200-1459071798_thumb.jpg

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you have other samples too? can you put other pictures too? also some very close up images. these samples are very interesting. we should find what might be :|

I only have those two, but there were more being sold at the Tucson show last month.

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My thought is that the “regular” and geometrical shape is due to the fact that these nodules were actually part of a greater and fractured septarian-like one, with the convex facets being the fractures among one piece and the other…something like that (though this is not agate).

ciao

Interesting idea, that might be plausible...I wonder about the yellow thing in the middle though...

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That could be due to a desiccation/dehydration process, considering that the inner part was organic, gelatinous or clay-rich and the outer part was stiffer. That's why the seller said it is septarian.

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

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That could be due to a desiccation/dehydration process, considering that the inner part was organic, gelatinous or clay-rich and the outer part was stiffer. That's why the seller said it is septarian.

I only have those two, but there were more being sold at the Tucson show last month.

Abyssunder so you think this might be a Geode with something organic in middle?

But a problem here. it is possible there are lots of them there and all same shape? i dont think something like this happens in Geode groups.

and someone cut them really nice for selling?

Sdsnl can you please take close up images? so we can take very close look at inner surface

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I'm leaning toward Septarian not Geode.

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

Thomas Mann

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I

im sorry im not very into these. is not Septarian a kind of Geode? i just read that from here:

http://meanings.crystalsandjewelry.com/septarian/

I think geode has an empty space in the kiddle with crystals surrounding it. Septarian has veins running in many directions and they are all filled upvwith crystals, no empty space. Their crystals are probably chemically different too?
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" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

Thomas Mann

My Library

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The septarian part seems to be clear now, but the symetric forms are still quite intriguing and enigmatic to me.

To me also!

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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Correct.

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

Thomas Mann

My Library

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The septarian part seems to be clear now, but the symetric forms are still quite intriguing and enigmatic to me.

Someone on Mindat said this: "Maybe it is silicate infilling on triple junctions produced by dehydration shrinkage in of some sort of sedimentary unit?"

I don't quite understand it, does it make sense to you?

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Someone on Mindat said this: "Maybe it is silicate infilling on triple junctions produced by dehydration shrinkage in of some sort of sedimentary unit?"

I don't quite understand it, does it make sense to you?

It makes sense for a single occurrence, but not for multiple replications with no variation.

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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It would make sense to me if the objects always had the same form and symmetry as in this case, which would account for the shrinkage at the same lines of stress having their starting points at the corners of the triangular form as the sediment dried out. It's the objects themselves which are a mystery to me. If they are corals, then the nearest in form which I can think of is Calceola, but that doesn't seem to fit either.

 

Greetings from the Lake of Constance. Roger

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It would make sense to me if the objects always had the same form and symmetry as in this case, which would account for the shrinkage at the same lines of stress having their starting points at the corners of the triangular form as the sediment dried out. It's the objects themselves which are a mystery to me.

Lud, this is exactly the point;

...why this pattern is not so common I don’t know...there must have been some special boundary conditions, but I think that the shape is primary and has been originated by the growth mechanism itself.

It’s a maximum/minimum problem: when the tension caused by the dehydration shrinkage is greater then the cohesion of the sediment, then the cracks start, but “soon” branch forming angles of approximately 120*, which provides the greatest stress relief with the fewest cracks. The growth is at right angle to the fractures, which would explain the convex shape of the facets, as a result of a vector sum of the growth in two directions (on a plane section).

To me, those pieces grew whithin an unconsolidated sediment with some triggering “singularity points” spaced out in the volume of a septarian-like body.

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Lud, this is exactly the point;

...why this pattern is not so common I don’t know...there must have been some special boundary conditions, but I think that the shape is primary and has been originated by the growth mechanism itself.

It’s a maximum/minimum problem: when the tension caused by the dehydration shrinkage is greater then the cohesion of the sediment, then the cracks start, but “soon” branch forming angles of approximately 120*, which provides the greatest stress relief with the fewest cracks. The growth is at right angle to the fractures, which would explain the convex shape of the facets, as a result of a vector sum of the growth in two directions (on a plane section).

To me, those pieces grew whithin an unconsolidated sediment with some triggering “singularity points” spaced out in the volume of a septarian-like body.

That explains it well, but given that cracks forming at angles of 120° provide the greatest stress relief, I don't understand why most septarian nodules don't crack like that?

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That explains it well, but given that cracks forming at angles of 120° provide the greatest stress relief, I don't understand why most septarian nodules don't crack like that?

just my thought…

in a “usual” septarian nodule the propagation of cracks within the hosting sediment allows a flattened (and cuspidate) pattern for the infilling material (veins);

what I can see here, is a failed (or early ending) cracking propagation, replaced by an almost radiating growth;

many hypotheses of why that happened in this case could be done…

ciao

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  • 7 months later...

I think I might have finally found an answer for this. I talked with a local paleontologist that makes frequent trips to Morocco. He identified these as a type of fan coral. He said they aren't cut and polished. Rather, each is an individual coral is polished on the top. He said they are Devonian and quite common over there. 

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  • 2 weeks later...
On 11/6/2016 at 11:49 PM, GeschWhat said:

I think I might have finally found an answer for this. I talked with a local paleontologist that makes frequent trips to Morocco. He identified these as a type of fan coral. He said they aren't cut and polished. Rather, each is an individual coral is polished on the top. He said they are Devonian and quite common over there. 

That is very interesting! Does he mean the septarian veins are casts of the coral, or should I look at it like a horn coral, with the septarian veins being hollow space on the coral that was later filled with minerals?

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4 hours ago, sdsnl said:

That is very interesting! Does he mean the septarian veins are casts of the coral, or should I look at it like a horn coral, with the septarian veins being hollow space on the coral that was later filled with minerals?

I was wondering the same thing. I personally know nothing about corals. I was surprised when he said they were "fan" corals. When I think of fan corals I think of the corals that look like THIS.

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