Search the Community

Found on a beach under a cliff , before i spend hours prepping do you think this is a crab? New to all of this so im not sure 20230210_201607.mp4

Greetings, friends. I have some very exciting news on a personal front: My first ever museum donation is this Mazon Creek Belotelsonid, which is going to the Indiana State Museum! Using advice from elsewhere on TFF, I reached out to their team a couple of days ago to ask if they might want it and surely enough they did!

Hello. I found three pieces in the Mazon Creek area that I’ve finally split open and am interested in. While there is a very good possibility that all three are just consequences of opening the concretion and not actually fossils, I figured I’d check. Image 1: I thought there was a slight possibility it was a leaf or a worm, but due to lack of detail, I imagine it is not. Image 2: Potentially the top of E. asherae or something similar. Image 3: I am actually just curious about what causes the small, light circles on the right side of the bottom piece and in the middle of the top piece. I’ve noticed these on many Mazon rocks and wonder if it is a mineral inclusion or something else. Thank you for taking a look!

Hello, I am new to fossil preparation but I bought one of those Miocene Crab concretions, but I am not sure how to separate the rock without damaging the crab inside. I only have dental tools and chisels, but they are not enough to separate the two sides for a pos/neg display that I could like. What sorts of tools could I use for the job? It is something similar to the picture below.

What I believe to be a carpus of the major chela of a ghost shrimp. Not an unusual find for me, but this was found near an exposure of Pittsburgh Bluff formation where previously I have only found them in Astoria formation.

Was very curious as to how this one came to look as it does. Any help is appreciated. Some of the photos are before and after a good cleaning.

Looking for help with this one, any input is welcome. Found in Grant County NM near the Gila National Forest.

Hello all! In my hunt to find crab concretions I started out at the beaches of the Olympic Peninsula. I wanted to share what I have found! I have gone three times so far and the close to six hour round trip was a bit rough, but very well worth it and I can't wait to learn and discover more. I am struggling to find crabs, but I am continuing my research and hope to figure something out soon. If there is anyone that could point me in the right direction that would be greatly appriciated as well! The first concretion I opened, It took no effort to crack. I speculate it could be a piece of bone? Wood? A super lucky find, I cracked this open after returning home and found leaf fossil concretion! I believe that these are not common on the olymipic peninsula?? I think they are Oak? Quercus? I believe a bivalve? I was confused with this one, could this be a parital crab carapace? Or the shell of a snail? And lastly this claw. Is it shrimp or crab?

Hello! I recently went to Mazon creek and was in the process of thawing my concretions when I saw this, and was wondering if y’all could help me ID it. I’m thinking maybe a shrimp, but am not very familiar with the fauna (or flora for that matter) of the area. Thank you!

My son picked this up while visiting his grandpa. We aren’t sure but know it’s probably a concretion. Would love it to be a real egg!

I wonder what do you think about this opalized ironstone https://www.mindat.org/photo-1239325.html can it be a wood?

Can anyone help figure out what these heavy rocks are?

I have tried looking up the difference between a concretion and nodule and can’t seem to get a clear answer. I have seen both terms used on the forum but don’t know the difference and would like a clear answer so I can know what I’m talking about. Thanks ahead of time!

I thought everyone in the Fossil ID forum would get a kick out of this one.

Hi folks, I went to the spoils pile with ESCONI pre-covid. I've had a bucket sitting out back ever since with concretions. Went through it today and banged a few together. I am not good at recognizing Mazon material, so I thought I would ask for some assistance here. I'm 99% sure 1A is a jellyfish, I haven't sorted out the name yet though. 1B appears to have some whiskers or antennae, so I'm hopeful it's some sort of shrimp or creepy crawly. The rest I'm kind of at a loss on. Any help appreciated!

Hello. I found this fossil matrix in my teens in an area of Northern California that's part of the Chico Formation. The surrounding sea shell fossils were in a layer of hard dark grey shale in a cliff face. I found this loose piece halfway down the hill up against a tree. I was told at the time that it's a concretion. I've never seen a concretion in person but they always look almost spherical in photos online. It weighs 5lb or 2.26kg Shaped like a sectioned log. layer of fossils running horizontal throughout what I've decided is the bottom. Sediment layers in various colors are ring shape above fossil layer, stay consistent from one flat end to the other. Any thoughts on if this was formed as a concretion and maybe how it got its shape? Thanks for looking!

Found this interesting rock and it has me scratching my head but it sure looks like some sort of egg or maybe the pit of a large fruit but then again it could be a concretion but I have my doubts about that. Hope these pictures have the clarity needed for good judgement.

The inside and the outside! What is this? Found in a bunch of river rock/decorative rock from who knows where.

Hello everyone! Today I ventured out to the Mazonia-Braidwood State Fish and Wildlife Area for my first time, and it was… something. This post is going to serve as both a journal of my day, and as a request for assistance as I try to figure out what exactly a concretion looks like. Once I got my permit outside the office (which is just down Huston Rd a bit from the IL-53 and Huston Rd intersection; this is for people like myself who struggled to find an address or location of the office), I headed to Mazonia south unit, where I went to fossil hunting site 3. There were not really any exposed rocks here, so I went deeper into the brush. I spent two hours picking up random rocks that looked remotely orange and red, until I realized that I was probably looking for the wrong types of rock in general. I had seen a ton of pictures online of concretions from Mazon creek, but all of them were of the fossils people found on the inside, which left me befuddled about what the outside looked like. I walked around until I found a place with cell service and planted myself on rock so I could watch a couple YouTube videos of people who had visited the area before. I learned a little about what I should be looking for, but I was still very confused. I managed to find the rock below, which looks vaguely like a fossil and gave myself some false hope, but I believe it’s probably just the way minerals formed on the rock that are deceiving: As morale dwindled, I made my way back toward the parking area and decided to walk a bit down the road. I found a neat little skull in a ditch as I was walking: As I kept going, I started stopping at some small exposures within a few feet of the road, and that is actually where I saw what I now understand to be the nodules I should be looking for. It was one of the two below: It made me feel a bit better that I found an actual concretion, as I went much of the afternoon without seeing any rock exposures. I have come to believe that fossil hunting site 3 may have a dearth of concretions, though I may be incorrect. Anyway, after finding the first concretion, I found a few similar rocks. However, I’m not entirely sure if they are potentially fossil containing material or if they’re just rock: They all have the dark red sections that I associated with iron, so I took them with. That is about the extent of what I grabbed that I thought were concretions, though I realize now that not all of those are even concretions. As I was wrapping up a mostly forgettable day, in the last roadside stop before my car, I came across this: I asked elsewhere on the interwebs and was informed that it might be a trackway, which I would think would be from an insect. However, if it is something else, please do let me know. Regardless, I was thrilled with this. I didn’t know what it was, but I did know it wasn’t something I had ever collected. In fact, today was the first day I have ever collected fossils from organisms that lived on land. It more than made up for the cold, gloomy weather and the disappointment I had experienced earlier. Just make sure to know generally what you should be looking for before you get there, unlike me. Now to my big question. How do I differentiate concretions from any regular old weathered rock? Are they typically round to some extent, as I see on others’ posts, or do they sometimes occur as jagged shapes? Are spherical rocks more likely to be regular rocks, whereas concretions are generally flatter in a dimension? I understand their shapes and sizes are diverse, but are there any patterns that tend toward a concretion over any a generic rock? As I finish up this topic, I do have one question about the two oval concretions I showed in my hand. Are the theoretical fossils inside the “egg” shape that lies inside the shell, or would they be on the outside of the egg shape? In other words, once I remove the rest of the shell from each of them, do I do the freeze-thaw cycles on the rock inside the shells? Thank you for reading and helping, and I apologize for all the questions!

Hi All I recently hiked to a remote area and only found one fossil, but it's a doozy! I've been wanting to find a shark tooth concretion since I heard about them so I was pretty happy when I found this concretion with what looked like a row of teeth and some cartilage in it. I don't think it's common for cartilage to fossilize this well so maybe the rostrum was really dense? I'd love to know what some of the shark tooth experts think about this one! I've started prepping it and there are numerous teeth still inside the concretion. I had to stop with the air scribe and move to acetic and B72 as they are all over the place and I don't want to risk damaging any. It's potentially an Ikamauius ensifer species, but that is still tentative. Of course I got it on video https://www.youtube.com/watch?v=dRXl8mGEIIM

Here is a video I just published that is just over 1 minute in length. Very funny too. I have an absolute blast putting this together. Enjoy

Hello- I am hoping to get some help with identification of a few concretions. These were all found in Mazon creek pit 11 area. Unfortunately, I was only able to find one side of these. The second to last may not be a fossil, but it has a really interesting/symmetrical shape so added it in just to check. I’m happy to take additional photos if needed. thanks in advance, this forum is always very helpful and knowledgeable when it comes to identifying! -tom

Hello, I am new here. I am looking for information on this concretion I found.

As it's too stormy to collect fossils... Jurassic, Callovian, Oxford Clay, Peterborough Member, Whittlesey, Cambridgeshire. This was something very odd I found from a concretion in the Oxford Clay. They are great for three dimensional fossils such as ammonites. It looks like wood, in which case it's my first bit that isn't carbonised, or possibly bone. It could also simply be mineral. Another possibility is fish. I really wish there was more of it, that might have cleared it up, and would appreciate your thoughts.

Hallo all, please can somebody help me with ID ? Cenoman ...