So I went hiking at Blanco County, Texas, and found this rock nearby a stream.
What kind of rock is it? And what are those little holes??
I tried the web and nothing! So maybe someone here is into Geology.
I'll post other angles.
My first guess is that they're small "potholes" formed by the erosive action of sediment-bearing water.
It could also be erosion caused by some sort of biological agent, like a boring organism such as a sponge. Potholes would still be my first guess though.
To elaborate on this, its possible that the rock contained readily dissolved minerals or coal fragments that were removed from the rock subsequent to its exhumation, creating small holes. The erosive action of the sediment-bearing water would have enlarged these holes as well as rounded them out. This would explain the morphology of the holes as well as their odd placement.
The holes seem to be clustered along some fissures in the rock, making me lean towards there being a significant chemical component to the weathering.
OP, wanna do an experiment? Pour a little vinegar on the rock. If it starts bubbling and fizzing, then it's a carbonite rock like limestone or dolomite that's highly subject to chemical weathering.
The experiment was as you predicted! The rock produced bubbles (mainly from those little holes) but most of all it fizzed.
I shot video, but the fizzing sound is not audible. Here's a screenshot of the video.
And here's a gif of one of the bubbles.
That looks a lot to me like a piece of fossilized seafloor, and what you have there are ancient worm burrows.
It could also, maybe, be depressions left from roots, but generally tree roots will also fossilize/petrify, and the rock itself really looks like it was once a soft mud. Still, this could have happened if the plant rotted out, pretty rare tho.
It's not gas bubbles, there is too much order. It's most absolutely not water erosion, >>7769229
is a complete idiot.
I would recommend walking around the area some more and looking for similar stones, you might get lucky and find something even more interesting.
Vinegar will fizz on just about any stone surface because of trace chemicals from the environment. Also if you want to get limestone to actually fizz, you need to use a stronger acid like HCl.
Hey... OP here
I'm no longer there at Texas hill country. I was visiting family and friends. But... I brought myself another rock. Here's the pic.
Another angle of 2nd rock.
Found both at the same area but not together.
Also both have strong odor of wet soil. Just something that caught my attention, as I've never found rocks or archeological debris abroad that smell. (My actual expertise is finding ancient ceramics and obsidian debris, but have only really basic knowledge of geology).
If I had to guess from these pictures, I'd say it's dolomitized limestone (>>7769294 & >>7769331 mentioned this already). Based on that, I'd say the holes are some sort of trace fossil.
It's hard to tell because of how weathered the rock is but those look like they could be diplocraterion, a trace left by a worm creature that lived in U shaped burrows.
Bit hard to tell, but I'd say that this is more of the same. The wet soil odor is probably because you got them from wet soil.
The right hand side of your sample looks "fresh", i.e. un-weathered. Image of that side please to help better identify it.
The anon/s suggesting limestone (sea-bed) are likely correct. Limestones are comprised of essentially 100% marine fossils. Mostly calcareous creatures like early corals and bivalves etc. In some cases beds and beds of organisms can be seen including 'soft' creatures like Crinoids but many get baked and are metamorphosed or get churned up by tectonic processes resulting in a soup of mashed up shell and coral so one can't always see any actual organisms like a rugose coral or whatever. Regardless, their composition is of mostly Ca type minerals all of which are easily consumed by acids and many predatory creatures (past and present) evolved ways to bore perfectly circular holes through protective shells to get to their prey hiding inside.
>>7769276 This anon's second conjecture is spot on, the first one however is not. The spherical erosion action creates what are called ooids. Ooids do not create the "potholes" and ooids usually only occur in lagoons with low temp variance. Also, if it were the result of sediment\bearing water erosion. you would have a Conglomerate with varied breccia sizes
Jesus christ everything in this post is incorrect.
I sincerely hope that you're just a precocious freshman and not actually doing geological work. If you are practicing geoscience then you're astonishingly incompetent and need to completely overhaul your understanding of sedimentology.
I'd expect a more factual analysis from a 1st year student. I'm 100% serious. You are a danger to the public if you are practicing geoscience.
not op but when we have strange stones
can any one give me informations about this stone
Seems this rock has created quite a buzz but not that much of a consensus.
I'm no geologist, but is it that difficult to pinpoint a rock with just a picture? Let alone the little holes. There were interesting theories though, and outside 4chan I was told it may be a sponge fossil.
Still... the debate may continue.