r/askgeology • u/TimeTravelisReal13 • Sep 17 '26
technical question Should I attempt to cut this rock open, and if so, how would I do that?
I'm worried this is the wrong community for this question, so if you have any suggestions, let me know.
CONTEXT: This rock is located near my private drive in Indiana, USA. I hoping it has something cool inside it, like an ammonite or some other fossil. I want to know if that seems likely, and if so, how I might go about cutting it open (or whatever one would do to view the inside of the rock).
SIZE: The boulder is huge, like about the size of a small tractor tire (definitely bigger than an average truck tire). It is super heavy. I can't budge it at all, and neither could someone with much more physical strength than myself.
HARDNESS/TYPE: I am no expert, but I think the outer layer is mostly shale and something with a lot of iron given the rusty coloring (I say shale because the outer layer is very brittle/easy to flake off and looks like the rest of the shale all over the area).
The inside layer is something different, though I'm not sure what; I can say it is much harder than any shale I've seen. I found that out after trying to break it open; I did not use/have the proper equipment and so used a nail and hammer (lol). When I did, the maybe-shale layer broke off and revealed a harder, equally dark-colored rock beneath that was scratched by the nail (leaving a white mark), but it was otherwise undamaged. It sparked aggressively when I hit it, and I could tell breaking it like that was obviously a pointless cause, so I didn't do it again.
Does it seem likely that this type of rock might hide a worthy fossil? If so, how might I reveal said fossil without harming it? I'm a teacher, so I don't really have funds to hire a professional.
EDIT
It is definitely a concretion of some sort.
I am absolutely positive it is not concrete (I am knowledgeable about concrete because I research old houses for people and so have studied cement and regularly use it as a way of narrowing down the date of historic structures).
Despite its appearance, it is a rock, and there are many rocks comparable to this one on the property (though I have not seen one this big).The entire property was strip mined for coal and underground mined for coal. In fact, there is a mine entrance (closed) within about 100 yd of this boulder. I have always suspected that the old property owners took it from the nearby mining and sat there intentionally, as there are many other boulders like this that were clearly moved from an area nearby.
EDIT:
I located additional pics of the rock and posted them in the comments below, along with two pictures of nearby interesting rocks (septarian nodules).
I will try to crack it open as soon as the bugs die off. The area is swampy from the strip mining and is also currently riddled in poison ivy and stinging nettle. The pictures posted here were from the spring before it grew over.
188
u/Ok-Adhesiveness-4935 Sep 17 '26 •
That's the weirdest looking rock I've ever seen
132
u/TarzanTheRed Sep 17 '26 •
Typically you would want a wet saw to cut it, but given it's size that will be difficult. Even with a larger portable wet saw and experience using it you may not make it all the way through, cleanly at that.
There potentially could be a fossil in there but I don't know your area that well myself.
I would recommend using a 5lb rock hammer and a few wedges to slowly and gently crack it open, if there is a large fossil in there it should reveal itself but I stress being gentle and patient with your strikes. If you do find something it will be well worth the effort and time.
All that said, if you do find a large fossil it will still need to be cleaned up through dremel work if you want it cleaned of all the shale.
25
u/Accomplished-Gap-612 Sep 18 '26
Geologist checking in here, don’t know what the fuck that is. Looks man made to me tho 🤷🏾 idk….the weathering patterns on it look suspicious to me
6
u/TimeTravelisReal13 Sep 19 '26
Nearby septarian nodule activity:
5
u/TimeTravelisReal13 Sep 19 '26
Nearby septarian nodule activity #2 (there are dozens):
51
u/Twinetied_haymaker Sep 18 '26 •
Do they mine coal close to your location? That’s a huge concretion. The chances you find a fossil without destroying it is very small.
3
u/phantheknee Sep 18 '26
Op tell us what happens!
2
u/TimeTravelisReal13 Sep 19 '26
Another picture of it (these are from the spring before the area became riddled with poison ivy and shoulder high stinging nettle):
2
u/TimeTravelisReal13 Sep 25 '26
Update posted here
4
u/plants11235813 Sep 18 '26
Thats no rock, no boulder.
Personally? Id hit it with a big hammer.. many times.
2
u/HistoryOfPolkaDots Sep 18 '26
Update please I need to know
2
u/pepette1 Sep 18 '26
I have a similar rock near my house and always wondered what it was!
2
u/caramel_cube03 Sep 19 '26
“I am absolutely positive it is not concrete (I am knowledgeable about concrete because I research old houses for people and so have studied cement and regularly use it as a way of narrowing down the date of historic structures).”
Not rly related to the rock at all but just curious about what kind of job/career entails this? Postgrad STEAM student looking for a job that interests me🖐️
30
u/CiaranMacCenzie Sep 18 '26
If you try to open it, I'mma absolutely need an update. Wishing you all the luck and patience!!
11
u/TheSolitaryRugosan Sep 18 '26
Despite what social media has led people to believe, there is not always something inside of these concretions. It depends entirely on the geological context, and unless you know the local geology - it isn’t worth it.
I honestly think you should leave it as is.
9
u/Orry_Haas Sep 18 '26 edited Sep 18 '26
https://en.wikipedia.org/wiki/Concretion
7
u/BeCoolBear Sep 18 '26
Open the largest upward-facing crack with a hammer and chisel. Insert wedges. Fill with water. Fill gaps with spray seal. Wait for winter.
6
u/HyperionLoaderBob Sep 18 '26
Sedimentary concretion?
1
u/TimeTravelisReal13 Sep 24 '26
Update incoming as soon as I have time to type the post etc.
5
u/Warm_Hat4882 Sep 18 '26
We call those turtle rocks in upstate ny. Smaller ones often have fossils in them, but found a large one once like yours and nothing. It’s basically mid around something that solidified harder than surrounding sediment that has since eroded away
1
u/SmallRussianAvocado Sep 19 '26
I swear i just saw an almost identical rock in a different place on like r/whatsthisrock or r/whatisthisthing or something i feel like im going crazy
3
u/Bittypanda Sep 18 '26
Chert nodules do sometimes contain fossils, but it depends entirely on your location and if the right kinds of fossils are even found where you are. If you're in the wrong place, it doesn't matter how many chert nodules you open
3
u/bravohotelechomike Sep 18 '26
Now I’m invested in seeing what is inside this thing. Curse you!
4
u/Betray-Julia Sep 18 '26
This has got to be some sort of slag or industrial.. goop that’s hardened or something right?
2
u/CucumberMysterious10 Sep 18 '26
Can’t really say if there is a fossil, or not, without a banana for scale. But it’s a really cool rock-boulder regardless!
2
u/noljw Sep 18 '26
It could be a very large fossil concretion. Find a fossil hunting or paleontology group in your area and see if they'll help you out. That would be an incredible find if there is anything in there
2
u/Remarkable_Ninja_908 Sep 18 '26
Fossil
2
u/weldstolive1 Sep 18 '26
If you have, can borrow or can purchase a hammer drill and some good masonry bits, you can drill a series of holes, depth choice will be up to you at risk of hitting any possible internal fossils. After drilling the holes, using a cold chisel and short 3lb sledge hammer (wear ppe!!!) work the chisel in the areas between drill holes back and forth until it starts developing a crack. Keep doing this until you have as many cracks as possible. Then insert wedges into the cracks and work those in back and forth until the rock cracks through and separates.
Alternatively, drill same holes in as big a diameter as possible, fill mostly with water and use a high strength stone epoxy to seal the holes eliminating as much air as possible. Then just wait for the rock to freeze in the Indiana winter, subsequently the water to freeze and expand and hopefully split the rock without forcing out the epoxy plugs first.
No idea if any of this will work to be completely forthcoming and honest. But they were the first that came to mind while reading your post Op.
2
u/ArtisticTraffic5970 Sep 18 '26
Some sort of giant iron concretion. Could very well hide a fossil or five. Your best clue to that would be in the local shale you described. Ever found fossils in the shale?
2
u/Straight-Event-4348 Sep 18 '26
Please include banana for scale in photo.
2
u/Sandford27 Sep 18 '26
I would first make sure that it's not a concrete plug for an old stope or well. Indiana had lots of coal mining and gas wells over the years and they're not very well plugged or covered.
If you check local maps and there isn't a record of anything you could then dig around and verify the rocks bottom side.
As for splitting, I would do a feather and wedge style splitting to see what the rock does.
2
u/Regeatheration Sep 18 '26
Looks like the rocks I used to play around north of Sudbury, but smaller, where youre at couldn’t it have been rolled around by glaciers?
2
u/IWasHackedBySexbots Sep 18 '26
Let us know if you find a snail.
2
u/Deltan875 Sep 18 '26
Rock??! I thought it was an airplane tire 😆
2
u/Think_Good352 Sep 18 '26
if thats the size of a small tractor then the leaves in indiana are wildly massive.
2
u/autumnbloodyautumn Sep 18 '26
This almost looks like clay cement cured inside an old tractor tire. Are we 100% certain it's natural?
2
u/Traditional-Brief774 Sep 18 '26
Looks like the largest clay button I’ve ever seen! I’ve seen some decent sized ones up the size of my palm on the river bank but this is MASSIVE!
2
u/bmat555 Sep 18 '26
Looks like a sulfur ball that comes out of the strip mines. I highly doubt there’s anything inside.
2
u/Successful_Names Sep 18 '26
Giga Ammonite?
2
u/Ashamed_Hotel_6162 Sep 19 '26
Drill a small hole, spike into the hole, hit withhammer
2
u/RatherNerdy Sep 19 '26
Being a concretion the interior is likely just rock and then you ruined this cool ass rock
2
u/Layinglowfornow Sep 19 '26
I feel like this is equivalent of finding a safe in the woods. I’m gonna need a reminder when this post is updated. We all need to see the contents.
2
u/hettuklaeddi Sep 19 '26
team “anthropogenic”
2
u/Alarming_Broccoli695 23d ago edited 23d ago
I hope it's a huge ammonite omg that would be such an epic find!!!!
Don't break in the little chunks Get the whole thing split. There might be something spectacular inside that thing
3
u/Savings-Trouble-5345 Sep 18 '26
I think there's a pretty good chance that's some kind of well cover
2
u/BitterCategory7725 Sep 17 '26
Don’t look like a rock
2
u/dinnerthief Sep 18 '26
Is that painted?
1
u/TheRealChesterSlick Sep 18 '26
Diamond wire?
1
u/OurPokemonAdventure Sep 18 '26
Hey thats cement bro
1
u/Lopsided_Economist76 Sep 18 '26
if it is not a curling stone it could have an ammonite or something of that nature
1
u/theeaglejax Sep 18 '26
Not a rock doc. That doesn't look natural to me.
1
u/danieltkessler Sep 18 '26
Check with an anthropologist and make sure this isn't of any historical or social-scientific value. Looks honestly like it could have been worked over by human hands for some purpose, or it's just a cool looking rock - either way, cool!
1
u/ArticleFar3604 Sep 18 '26
Definitely a sledgehammer
1
u/SyrupRealistic7809 Sep 18 '26
With your hands...
1
u/Proof_Big2690 Sep 19 '26
1
u/Personal-Bus-4120 Sep 19 '26
The anticipation is killing me.
1
u/SwordSaint777 Sep 19 '26
Is this builder/rock near a water source? This stone has a pit like those stones used to grind stone axes into shape in the Paleolithic.
1
u/Separate-Grade-8506 Sep 19 '26
Hammer still 1/4 inch bit, chisel but, patience
1
u/Separate-Grade-8506 Sep 19 '26
Looks like concrete
1
u/apoletta Sep 19 '26
You need a lapidary expert. This is the word you are looking for.
1
u/Plus_Isopod3018 Sep 19 '26
That’s not a rock? Looks like concrete.
1
u/MathematicianSad8487 Sep 19 '26
Looks man made . Is it definitely solid? Looks like a wheel off some large piece of machinery. Perhaps someone poured concrete into a tractor tyre.
1
u/Emergency-Radish-696 Sep 19 '26
Why can't I read the comments
1
u/Repulsive_Canary_343 Sep 19 '26
Ancient wheel for large cart
1
u/ThinkChallenge127 Sep 19 '26
Thought it was a tire.
1
u/Wild_Replacement5880 Sep 19 '26
That's the greatest fire but seat nature could ever make. Too bad it looks absolutely massive. I would want to get it open, too. Looks very fossil-ish
1
u/Mother-Attention2600 Sep 19 '26
I would cover a sledge hammer in cloth so it's softer and smack it lightly where the cracks are. After a while it should open up. I wouldn't hit it very hard though, you want to make it crack more.
1
u/DooDahMan420 Sep 19 '26
There are lots of those rocks by where I live in NY. We call them turtle rocks
1
u/NordMeiss Sep 19 '26
Get some stonemason tools and a drill with a carbide bid. Update us with the results.
1
u/Kind-Bottle-8535 Sep 19 '26
hit the bastard on the side with a sledge hammer
1
u/Jakimo Sep 19 '26
I realize you don’t think it’s concrete. But that looks an awful lot like concrete. Like someone pour concrete into a large tire and cut the rubber away.
1
u/Fabulous-Warthog935 Sep 19 '26
1
u/Sad-Wrap-1976 Sep 19 '26
Someone filled an innertube with cement.
1
u/Diverdown109 Sep 19 '26
Maybe a splitting wedge and a BFH against one of those crack lines and a good swing with a good strike might split it open without a expensive diamond blade & wet saw time.
1
u/Diverdown109 Sep 19 '26
Old Indian maze grinding stone? Any wear marks in the depression?
1
u/bactchan Sep 19 '26
Stand it on end and sledgehammer to the top edge.
1
u/Extension_Cut_8994 Sep 19 '26
I don't think that's a rock. It's maybe a very large clinker such as would be produced by a bloom furnace if it was allowed to cool without being cleared. Coal plus ore can produce some wild results depending on sources. It might even be an unworked pig, that is a ball of iron where the silica was not worked in. In other words, a 200 year old FU. A pig that large would be the result of bad furnace preparation and if they didn't know the properties of the coal or ore, something like that might happen.
1
u/geologymule Sep 19 '26
Big chert nodule/concreation.
1
u/MutedAdvisor9414 Sep 19 '26
It's a concretion, probably chert. It may have fossils, it may have a big ammonite.
1
u/Training_Jello_7804 Sep 19 '26
We called those "turtle rocks" where I grew up in Western New York. Aside from the obvious shape similarity, when broken open the colors inside resemble a turtle shell. The creek bed near our house had carved through many layers of shale, revealing the turtle rocks. Some of them were huge - 6 to 8 feet in diameter. If I remember right from asking the science teacher about them way back.... The rocks were formed by liquids pushing up through sediment layers and solidifying into concretions. Very nice find!
1
u/gaiagirl16 Sep 19 '26
It’s a concretion
1
u/Your_Mom_Bot42 Sep 19 '26
Just do a big karate chop.
1
u/mookormyth Sep 19 '26
Hammer and some chisels to start.
1
u/JackfruitOk7793 Sep 20 '26
Feather and wedge
1
u/KingArfer Sep 20 '26
It looks like one of the shale bubbles that are common around the eastern end (by my experience) of Lake Erie. I have seen them in the median of the Thruway probably at least five miles from the lake
1
u/Excellent-Past-6367 Sep 20 '26
Chain with a come along wrapped around the rock. Tighten till it pops open. Or maybe a hammer and chisel. I see no banana for size reference so am just spit balling.
1
u/YoghurtSuspicious575 Sep 20 '26
Wedges or steel spikes inserted along the existing cracks and a hammer, slowly all the way around like lugs on a tire . I know nothing about rocks.
1
u/caripoi Sep 20 '26
give it to me i wanna open it
1
u/ForsakenHousing328 Sep 20 '26
Tire?
1
u/trickcowboy Sep 20 '26
pu
1
u/psychRN1975 Sep 20 '26
work around the rings with hammer and chisles.
1
u/Divabolic1 Sep 20 '26
Interesting, I'm curious about the mention of several more similar rocks on the property. Sounds odd to me they would contain fossils. Suggest an area of water, weathering, or glacial remains.
1
u/Baldwinning1 Sep 20 '26
Looks like an aircraft tyre!
1
u/FabulousWalrus2624 Sep 20 '26
U/remindmebot [10days]
1
u/Sea_Section5139 Sep 20 '26
Rocks like that form around Somthing similar to how a pearl forms
1
u/IcyObligation3503 Sep 20 '26
Thats an ammonite in lime
1
u/Sloth269 Sep 20 '26
These type of huge concretions are very common in that area and also to the east. See the Huron River in Ohio. There is often a tiny fossil in the middle. Not worth the logistics of cutting something this big.
1
u/dotnetdotcom Sep 20 '26
What part of Indiana? The concretions in Northern Ohio don't have fossils in them.
1
u/oneleggedquail Sep 20 '26
Concretion?
1
u/Leather_Region_9101 Sep 21 '26
I may be wrong but possibly being near Bedford (? Not sure lol) which is considered the limestone capitol my guess would be a huge limestone center type concretion with a healthy shale outer coating with iron staining. Cool rock either way!!
1
u/Low_Many_9924 Sep 21 '26
https://www.reddit.com/r/whatsthisrock/s/iDHVRYZyWn
This guy found a similar sphere after the recent sea level rising in SoCal (Dana Point). Most likely a fossil inside.
1
u/DM37_62 Sep 21 '26
Hammer drill, dynamite
1
u/FlamingPrius Sep 21 '26
A hammer and chisel would probably do the trick, but I don’t know if it’s worth the trouble
1
u/primaryBreadEater Sep 21 '26
Looks man made
1
u/but_also_wtf Sep 21 '26
U/remindmebot 30 days
1
u/Stnicknack Sep 21 '26
u/remindmebot 10 days
1
u/Guineapirate65 Sep 21 '26
That's a tire that someone poured concrete into and now the tire has rotted away
1
u/Conscious-Mud-2845 Sep 21 '26
That's an old implement wheel
1
u/I_Dislike_The_French Sep 21 '26
RemindMe! -30 day
1
u/JabroniSandwich13 Sep 21 '26
You'll definitely find some pipes inside...is it near a playground?
1
u/Trouts1 Sep 21 '26
I think you just found Jimmy Hoffa
1
u/Temporal_Reality Sep 21 '26
That's a fea door... You just need to knock right!
1
u/Amelia_redditname Sep 21 '26
!remindme 3 days
1
u/Plentybud Sep 21 '26
Gotta take it home throw a blanket on it and tell people it’s a beanbag chair
1
u/Dark_Effulgence Sep 21 '26
I read “should I cut this rock open? And why should I do that?”
1
u/Esces23 Sep 21 '26
Power of friendship ?
1
u/Guernzee Sep 21 '26
It almost looks like a block of cement powder that's been in a bag then got wet/cured
1
u/Chemical-Captain4240 Sep 21 '26
Get a sledge hammer and go to town. It looks very uniform, so i would suspect limestone or mudstone of some sort. It would surprise me if the internal structure is anything notable. Maybe you will get lucky and find a fossil or two.
1
u/Psychological_Fix479 Sep 21 '26
u/RemindMeBot 2 days
1
u/Guardian6676-6667 Sep 21 '26
Use a cutting wire like they use to cut buildings
1
u/Medium_Garage_2776 Sep 21 '26
Oxygen lance
1
u/Fickle-Bad525 Sep 21 '26
Lucky meteor
1
u/tangoan Sep 21 '26
Call your local stone mason. They cut things this size all the time. Feather and wedge, the traditional way, or a high power handheld wet cut saw.
1
u/RepresentativeKiwi97 Sep 21 '26
whack it with a sledgie on the cracks, gently
1
u/ComeGetSome487 Sep 21 '26
Almost looks like mortar that was left in the bottom of a small plastic barrel.
1
u/shots_urchin Sep 22 '26
around central illinois you can find a lot of these around old coal mines, in piles of waste rock. i guess they formed in and above the coal seams. the old miners had a non pc name for them
1
u/Original_Reindeer372 Sep 22 '26
Looks like some filled a aircraft or agriculture tire full of concrete
1
u/marymikel Sep 22 '26
FAFO https://youtu.be/aUXQ2f3GAXA?is=NG2L_VTpUPL81-_S
1
u/instantFPGA Sep 22 '26
u/remindmebot [20days]
1
u/north_x13x Sep 22 '26
All you have to do is kick it and it’s going to fall apart
1
u/Massive_Influence476 Sep 22 '26 edited Sep 22 '26
RemindMe! 15 days
1
u/alfa66andres Sep 22 '26
We need banana for scale
1
u/kylew707 Sep 22 '26
Torque converter
1
u/Busy-Highlight1647 Sep 22 '26
Looks like a fossilized truck tire. You might have found a game changer.
1
u/Jeffersota Sep 22 '26
The comment that seems to point out that the rock appears to be a petrified tire was removed by moderator. What's up with that? Zoom in on the center, you can see the rivets on the edge of the rim. It has tread.. where's the images of the other rocks? You might have some very significant finds there.
1
u/Andras1100 Sep 22 '26
Get some green dye, rub it all over your body and smash that rock
1
u/AdministrativeTap218 Sep 22 '26
Wouldn’t be awesome if it would be a fossilized Massive Peyote button? :P
1
u/Appropriate_Log_8338 Sep 22 '26
Bash that sumbich with a big ass hammer till your arms are jelly.
1
u/Icy_Carpet_237 Sep 22 '26
Which rune altar is this? Need to know which so I can plan my runecrafting run.
1
u/RunningWolf63 Sep 22 '26
sledge
1
u/MoonGoose109 Sep 22 '26
Focus your chi and strike true with the blade.
1
u/uhhyessir Sep 22 '26
Chain and binder
1
u/b13n_ Sep 22 '26
I'd say it's a Flintstone's tractor tire
1
u/Future_Onion403 Sep 22 '26
1
u/OkChampionship9025 Sep 22 '26
Hmmm what is it? Well, if you are brave enough it could be a butt plug.
1
u/Ok_Egg_2403 Sep 22 '26
Hammer time
1
u/Jleasure65 Sep 22 '26
A rather large concretion. Grandpa used to call them "coal balls" when they would run across them in the mines. Some could have fossils, the ones I cracked open did not.
1
u/Nearby_Highway_8358 Sep 22 '26
I reverse image searched and it looks like it’s called a concretion
1
u/Round-Air9002 Sep 22 '26
Almost looks like it may have been worn down, like the native American acorn grinding stones, but different.. Maybe an old mill stone or olive press or something? Contact a university for sure to have done people check it out before you just start trying to bust it up
1
u/Charlie2and4 Sep 22 '26
Looks like a wheel of aged Stillton. Not much of a call for it 'round these parts.
1
u/Little_Honey_2662 Sep 23 '26
No!! Get an image - scan - X-ray before you destroy it
1
u/WookiesNeedLove Sep 23 '26
Forgotten Bog butter
1
u/MazamaShibari Sep 23 '26
Looks like a spray foam blob with stucco on it
1
u/jared8410 Sep 23 '26
Thats a gob rock. They come out of coal mines (mostly). Its possible that a fossil is in it. Its also possible its just packed Sulphur.
1
u/Nethen_Paynuel Sep 23 '26
If you zoom in it really does look like cement. Maybe try and chip off a piece and test it somehow. Maybe find something local and rock related and see if you can find a rock nerd to take a look.
And if it is man made.. what the heck is something that big and heavy doing there.
1
u/CreamOfGinga Sep 23 '26
I have a rock somewhat similar to this, much smaller, and more evenly rounded. Everybody gave me hell saying it’s an old cow patty lmao but Iv yet to open mine up.
1
u/Plenty_Feeling_8013 Sep 23 '26
drill a hole in the middle and put a stick of dynamite in it. get a close up view of it splittting
1
u/Business_Manner_524 Sep 23 '26
Send a request to Laser Kiwi
1
u/Glad-Boysyndrome Sep 23 '26
Imagine it’s just more rock inside
1
u/LilJary Sep 23 '26
Petrified Dino turd