South Texas Upper Cretaceous Coral

[CraigHyatt]

I see these all over the place and wonder what they are. They all have the same surface crazing and pitting. Color varies brown, orange, pink. Attaching a photo of the surface and the inside after a good hammerin'.

[CraigHyatt]

Should point out that a lot of the rocks out here have fungal infections, but I don't think that's it.

[CraigHyatt]

Also, when I see these concretiony looking exposures, is that a sign there might be good stuff nearby?

Edit: Basically I want to find something new besides ammonites and oysters. ;-)

Edited May 19, 2016 by CraigHyatt

[gavialboy]

those are some awesome finds. congrats on finding them although i am not sure what they are sorry i could not be of any help

[Fossildude19]

Looks like more weathered chert there Craig.

Not seeing anything biological in origin in the last pic.

Keep looking - you are becoming more familiar with your area - it's good watching you learn.

Regards,

[tmaier]

What you are seeing above is all the things that happen when calcium carbonate dissolves and becomes redeposited. The first object looks like a chert nodule, which are created when water dissolves the carbonate and then the solution become saturated, and the mineral precipitates back out to form sheets, crystals, and nodules. The limestone was the original, primary precipitate of calcium carbonate. The chert forms later. Sometimes the limestone contains fossil, and they dissolve out and create a void. Or sometimes the void is not caused by a fossil, you have to inspect them. Sometimes the void becomes filled with saturated calcium carbonate and become a cast of the void, so you can find fossils that are pure chert. So where you are poking around there might contain fossils, but looks like it also contains many artifacts of limestone that has been dissolved, so you will find many fossil-like voids and other artifacts of the solubility of calcium carbonate.

[doushantuo]

Tmaier,you sure know your silica diagenesis

Whenever,someone says chert,i get this urge to send PDF's.My doctor ,who doesn't know chert from shirt, tells me not to worry .That's what he also told me right before the brain transplant,and look what has happened.

https://www.researchgate.net/publication/275964349_Astronomical_forcing_of_a_Middle_Permian_chert_sequence_in_Chaohu_South_China

https://www.researchgate.net/publication/230451037_Chert_occurrences_in_carbonate_turbidites_examples_from_the_Upper_Jurassic_of_the_Betic_Mountains_southern_Spain_Sedimentology

https://www.researchgate.net/publication/251449948_Chapter_3_Silicification_of_Continental_Carbonates

https://www.researchgate.net/publication/230364535_Silicification_and_dolomitization_of_anhydrite_nodules_in_argillaceous_terrestrial_deposits_An_example_of_meteoric-dominated_diagenesis_from_the_Triassic_of_central_Spain

flint nodules,Cretaceous of France:

https://www.researchgate.net/publication/262304537_Inclusions_of_conifers_echinoids_foraminifers_and_sponges_in_flints_from_the_Cenomanian_of_Charente-Maritime_France_Contribution_of_synchrotron_microtomograph

Edited May 20, 2016 by doushantuo

[tmaier]

Doh! I made a mistake above. Chert is a precipitate of silicon, not calcium carbonate. What was I thinking? It's early and I'm still waking up. =-( The calcium carbonate does precipitate out to form similar nodules, and you can tell the silicon ones from the carbonate ones by seeing if they react with vinegar. The carbonate will react, the silica will not.

[CraigHyatt]

Doh! I made a mistake above. Chert is a precipitate of silicon, not calcium carbonate. What was I thinking? It's early and I'm still waking up. =-( The calcium carbonate does precipitate out to form similar nodules, and you can tell the silicon ones from the carbonate ones by seeing if they react with vinegar. The carbonate will react, the silica will not.

That's funny. I just pointed johnnyc over here because of the similarity of his sample to mine. Now I'm even starting to wonder if the red voids in his sample might not be artifacts. Here's his sample next to mine. Can't paste the link to his article for some reason. It's "ID possible dino bone from Morocco".

<------- JOHNNYC ---------> <------------ CRAIG ------------->

Edited May 20, 2016 by CraigHyatt

[tmaier]

Red and brown are often signs of iron that got dissolved and carried into the matrix. Iron has a lot of oxidation states that give it different colors. This is an example of a good time to look at other materials from the site and look at what the primary materials were, and how they have morphed over time. If you can find specimens that you know could not be bone, yet have the same characteristics (like the porous and layering we see here), then it gives evidence that it is just a mineralogical formation and not likely petrified bone. Normally a beginner fossil hunter will grab what looks like fossils, and totally ignore examining the other rocks themselves, and that is how you end up with a lot of mysterious specimens that are difficult to interpret. If you are unsure, then start reading the rocks at the site. I'm not really good at determining bone, but my guess is that the above photo is not bone. Your specimen at the top photo of this thread is definitely chert or calcium carbonate nodule. It has an outer "rind" that is the mixture of the limestone with the precipitate, and that is normal at the boundary layer of the two.

[CraigHyatt]

Red and brown are often signs of iron that got dissolved and carried into the matrix. Iron has a lot of oxidation states that give it different colors. This is an example of a good time to look at other materials from the site and look at what the primary materials were, and how they have morphed over time. If you can find specimens that you know could not be bone, yet have the same characteristics (like the porous and layering we see here), then it gives evidence that it is just a mineralogical formation and not likely petrified bone. Normally a beginner fossil hunter will grab what looks like fossils, and totally ignore examining the other rocks themselves, and that is how you end up with a lot of mysterious specimens that are difficult to interpret. If you are unsure, then start reading the rocks at the site. I'm not really good at determining bone, but my guess is that the above photo is not bone. Your specimen at the top photo of this thread is definitely chert or calcium carbonate nodule. It has an outer "rind" that is the mixture of the limestone with the precipitate, and that is normal at the boundary layer of the two.

Agree. We were trying hard to figure out the mineral in his samples independent of whether his samples were bone or not. We were trying solubility in water, vinegar, hardness, etc. I like trying to solve mysteries like that. :-)

When I saw a closeup of the chert samples, I was struck by how much they resembled his samples. Almost a waxy appearance with the same sort of fracture characteristics.

Then, when I saw the red dots in my samples, I started to thing the red voids in his samples might not be vascular, as we were guessing. I was trying to come up with elaborate theories about how the channels might have formed as the marrow ossified, but I was never really happy with them.

Now that I understand about how my samples formed (thanks!) I think the simpler answer for johnnyc's samples is that the voids are just part of the mineralization process (i.e. iron oxide + gas voids) and not any sort of biological structure.

Man, I love this stuff. I did engineering and research for decades, but I've been so bored since I retired. All this fun stuff is bringing me back to life. And mama's happy because I'm not whining and moping around the house. Also, since I'm bringing home stuff that actually looks like something, she's starting to get interested in it herself. She's a dentist, so maybe I can get her to chip in on the fossil cleaning. ;-)

[digit]

Doh! I made a mistake above. Chert is a precipitate of silicon, not calcium carbonate. What was I thinking? It's early and I'm still waking up. =-( The calcium carbonate does precipitate out to form similar nodules, and you can tell the silicon ones from the carbonate ones by seeing if they react with vinegar. The carbonate will react, the silica will not.

And I thought you were just doing that to see if I was awake while reading it. I'm guessing the presence of all those nice chert nodules in Craig's area of Texas are what the Native Americans used to make some of those lovely worked projectile points, knives, and scrapers that I've seen from Texas. Those artifacts intrigue me and make me want to go to Texas to look for them (but not till the heat of the summer is well past). While collecting pieces of chert formed from silicified fossil corals in southern Georgia I was able to find two broken pieces of what are called Hernando points--and a lot of flakes (debitage) which I find fascinating as well. Fossils or artifacts or minerals--I'm always up for a hunt no matter what the quarry.

Cheers.

-Ken

[tmaier]

"voids are just part of the mineralization process (i.e. iron oxide + gas voids) and not any sort of biological structure." Yeah, I think it was a void and became filled with a mineral precipitate. His is grainy, and yours is more like glass, though. His might be a silica or a carbonate. The specimen overall looks like bone, but the white stuff is an artifact of the void, in my amateur opinion. I also have an R&D background, and did electronics and programming most of my life. In my early years I was a chemistry major, and worked in analytical chemistry. I've also worked in physics and biochemistry and other fields, as technical support for research. And I worked for industry doing design. I like unraveling the unknown, too. I got bumped out of work a bit early, and am being "retired" because I'm not keen to find another job. At my age, employers are not eager to hire me and I don't want to move. But I miss solving puzzles, and biology and paleontology were always a fascination of mine, so I hang out here trying to identify fossils. =-)

[CraigHyatt]

Yeah. Very similar backgrounds. We moved down here in the middle of nowhere for my wife to take a government job running a clinic. I had to quit a job that I loved, and there are no research jobs (or universities to speak of) down here. We are only stuck here for a couple more years, and then we can move back to civilization, but I figure after 40 years of busting my butt, I deserve to have some fun. ;-)

Once we are in range of a university, I will likely go take some courses in geology or paleontology. It's actually good that I'm getting some hands on experience first. That way, the courses will make a lot more sense. Meanwhile, I'm having a blast on the forum and learning so much.

[tmaier]

Ken... "Fossils or artifacts or minerals--I'm always up for a hunt no matter what the quarry." I go out to just study nature in general, and find fossils and other things just by accident. The way I hunt fossils, I always win because even if I find nothing in the fossil category, I most likely found something else of interest. I once met some Appalachian Trail hikers and when out on a day trip with them, and found out they were hiking warriors. I was poking along looking at the rocks and plants and animals. They never invited me along again, and that feeling was mutual, because they were passing right by all kinds of interesting things and would not pause to look. They had the attitude that they were conquering the trail, and I had a hard time keeping up with them. Not my type of nature hike. =-)

[digit]

Sounds like me if I have a camera in my hand. I'm always the one trailing so far behind that I'm out of earshot of the tour guide. Same way underwater--lose divemasters within minutes. I enjoy going out on hikes to see what interesting things might pop-up along the trail. Those are more "passive" outings where I let nature set the schedule and provide the entertainment. When I'm out on a "hunt" it is much more "active" in that I have traveled to a specific location with the intention of finding something--minerals, antique bottles, fossil concretions, etc. Each type of hunt has its own unique skills, challenges, and rewards and though I usually come home with a bag (or sometimes suitcase) full of finds, the true treasure for me is the experience of being out on a mission to find something. This is why I don't buy fossils--without the experience behind them the objects are meaningless and hold no value for me.

I also have a similar background in that I left a high paying job in Chicago to work with a new (at the time) non-profit group in Florida that was popularizing "fish watching" for divers in the same vein as Audubon bird watchers. I soon learned that there were few job opportunities for interesting computer programming work in the corporate world in South Florida and "retired" myself some two decades ago. I now work with a variety of organizations combining my computer skills and love of nature (particularly marine biology). I'm busier than I ever was at a 9-5 career but having much more fun (and varied experiences). Wouldn't recommended it as a way of life for most folks but it works for me.

Cheers.

-Ken

[doushantuo]

Great to see paleontology and fossilhunting having a positive effect on people's lives.Not in my case.Paleontology has turned me into a raging monster stuffing literature down peope's throat.I turn red in the face when people place the Praguian in the Jurassic.In my dreams I am chased by people who shout "Brontosaurus" and "Dinichthys",and i wake up in a cold sweat.Last week I turned over the science page of a well-respected national newpaper,reporting on graptolite extinction.Some one had put a photograph of a 3D preserved graptolite there.It sort of looked like its thecal spines were legs it was standing on. The article called the graptolites "shrimp-like".No i didn't contact the author of course,

Because of the restraining order

Meanwhile :

williamsilicadiagenejsr1985.full.pdf

Edited May 20, 2016 by doushantuo

[CraigHyatt]

Interesting to me that fossil hunting attracts so many engineers. :-)

[digit]

Great to see paleontology and fossilhunting having a positive effect on people's lives.Not in my case.

Sounds like you need to take it easy--maybe go out and do some fossil hunting?

I have to work hard to control my OCD which demands that I correct mistakes where I see them. Comes in handy when I do some avocational copy editing for friends who are authors but difficult to keep under wraps when I have just enough knowledge to recognize mistakes (luckily I'm still mostly a noob when it comes to fossils that I don't have to fight that urge much on TFF).

To direct the topic back to its roots, I'm now turning my thoughts more to collecting silicified coral chert in the Withlacoochee River as the Peace River seems to have turned off the lights and locked the doors for this season. For the benefit of readers who didn't get to see my earlier posts on hunting silicified corals (and tumbling some into interesting forms) I provide these links:

http://www.thefossilforum.com/index.php?/topic/48828-first-coral-hunt/

http://www.thefossilforum.com/index.php?/topic/58339-silicified-fossil-coral-tumbling/

Cheers.

-Ken

Interesting to me that fossil hunting attracts so many engineers. :-)

I wonder if the methodical personality that seems to be beneficial to engineers and scientists just transfers over well to fossil hunting? That being said, there are some people on this forum with some wonderful (and to me unimaginable) artistic skills. I've seen some paleo-recreations and restorations on this forum that leave a smoking gaping hole where my cerebral cortex once resided. The only thing I can do that is marginally artistic is photography and I've tried to develop that rather than working on drawing identifiable stick figures (beyond the limit of my skills with paper and pencil).

[fifbrindacier]

Great to see paleontology and fossilhunting having a positive effect on people's lives.Not in my case.Paleontology has turned me into a raging monster stuffing literature down peope's throat.I turn red in the face when people place the Praguian in the Jurassic.In my dreams I am chased by people who shout "Brontosaurus" and "Dinichthys",and i wake up in a cold sweat.

Wow