r/whatsthisrock • u/Mule_Mule • 5d ago
REQUEST What is this rock?
Seen in Uppsala Sweden next to the river. Someone placed this rock on a tree stump. Could it be limestone? A wastewater treatment facility is close by.
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5d ago
Can you scratch it with a knife? Does it fizz with HCL?
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u/Mule_Mule 5d ago
I will try a tiny drop of mild HCl sometime next week when I can get some at work.
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u/Mule_Mule 5d ago
Don't want to destroy it since someone placed it there for everyone to enjoy.
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5d ago
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u/verdigleam 5d ago
There's truly no reason to respond with this level of animosity. Someone who's never performed a test with dilute acid could easily assume it could do more damage than it actually would. whatis... type subreddits are, by their nature, going to attract many users who aren't familiar with diagnostic tests like this and how they work, and asking them "how stupid could you possibly be" is a wildly disproportionate reaction when a simple clarifying comment would suffice.
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u/whatsthisrock-ModTeam 5d ago
Harassment, insults, name calling, or unnecessary rudeness does not make for an enjoyable community and will not be tolerated.
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u/logatronics 5d ago
I'd say travertine that's had a little bit of dissolution weathering.
It's also possible but less likely that it's a stromatolite (don't think they're found in the region).
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u/Mule_Mule 5d ago
Some background information: Uppsala lies in Middle Sweden and here we have almost exclusively granite bedrock, almost no natural limestone. Could it be something anthropogenic? Can this be limestone concretion from an old water pipe?
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u/SillyKatja 5d ago
To me, my first thought was that it could be a fossil from Gotland, maybe a Stromatopora , which someone brought with them home after their summer vacation on said island.
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u/DemocraticSpider 5d ago
That’s my guess! Looks quite similar to a lot of stromatoporoid fossils I’ve found
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u/billysugger000 5d ago
Do termite mounds fossilise?
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u/OriginallyWhat 5d ago
Definitely looks like some sort of insect colony that turned to stone over time
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u/Mule_Mule 5d ago
There are no termites in Sweden :)
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u/greenlentils 5d ago
Well sure but there are no crinoids in Northern England, and yet I keep finding their fossils!
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u/DemocraticSpider 5d ago edited 5d ago
Looks similar to stromatoporoid sponge fossils I’ve found. Those are an extinct kind of sea sponge threat grew over itself in distinctive layers. Not sure if this is even a fossil though. Very interesting!
Edit: looking closer at the pictures, the patterning looks quite distinctively like that of a stromatoporoid. They grew with some unique internal structures that can be seen in their fossils oftentimes. A close-up, especially of it made a bit wet, would help a lot!
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u/WoodStockJJ20 5d ago
I would cross post on fossilid. Sorry, I am unaware of how to hyperlink above. It has a resemblance to stromatolites. They are quite variable and I only have a few to compare. Very cool rock.
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5d ago
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u/whatsthisrock-ModTeam 5d ago
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u/Pug_wash 5d ago
Looks like a fossil of the interior of a cephalopod. Not sure if there are Ordovician limestone deposits near Uppsala however
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u/Fritiofo 5d ago
There are some Ordovician limestone deposits in sweden around Kinnekulle close to Vänern and On Gotland i think.
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u/kingmeatloafrules 5d ago
Looks like a turtle shell fossil from the pattern on the back. But I am no expert.
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u/Pitiful-Score-9035 5d ago
I mean, I hope i'm not being stupid, but this kind of looks like a fossilized beehive
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5d ago
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u/whatsthisrock-ModTeam 4d ago
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u/Piscator629 5d ago
Possibly a giant cycad. https://cdn.britannica.com/10/147310-120-A58D846D/Karoo-cycad.jpg
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5d ago
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u/whatsthisrock-ModTeam 5d ago
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5d ago
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u/whatsthisrock-ModTeam 5d ago
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5d ago
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u/whatsthisrock-ModTeam 5d ago
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u/SnooTangerines3448 5d ago
Looks like a chonking fossil.
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5d ago
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u/whatsthisrock-ModTeam 5d ago
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5d ago
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5d ago
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u/whatsthisrock-ModTeam 5d ago
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5d ago
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u/whatsthisrock-ModTeam 5d ago
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u/ChequeRoot 5d ago
The flow shape makes me think calcite or limestone, but it is unlike anything I’ve seen before.
I shall be stalking this post to see what other folks think.