I have had this for a long time. Found it camping in the Midwest, I don’t know specifically where. It is Nonferrous. Weight 465.1 grams. Displacement in water approximately 115 cc. It is very dense (heavy for size). Smoothish dark brown exterior. The 'bowl" is slightly lighter in color.
Photo’s attached…sorry, my posting skills suck.
Nobody I have asked seems to know…somebody suggested Tektite.
Not a tektite.
Whatever it is, possibly carved out by someone for some use?
Some macro photos of the texture of various areas would possibly be helpful, as close as you can get.
Nothing really suggestive to me of it being anything other than a splendidly contorted rock, rather than a fossil. Also nothing suggests it has been worked by humans in any way before ThisSpaceForRent picked it up.
If igneous, which seems reasonable from the pics, then one option for the big indent is that it was part of a gas bubble, now partly exposed as the rock has tumbled in water.
Really, really hard to tell what kind of rock it is based off those photos, but props for putting a ruler in the photos.
It has elements of both a ventifact (the dark surface polish, the slight faceting on some surfaces and general lack of rounding) and a fluvial pebble (the hole - even if it was a gas bubble originally, it’s been subsequently smoothed over).
Usually, when I see that combo, the words glacial and periglacial come to mind. Those can be pretty arid environments, allowing for some characteristics like “desert varnish” and ventifact faceting to develop outside their usual locations. I’m even seeing what looks like some incipient salt pitting.
Whereabouts in the Midwest did you find it, in general terms rather than specifics? State or rough area?
My Little Golden Guide of Fossils identified most such objects as concretions, generally spheroidal rock shapes often taken for fossils, but not really the remains of organic life. Hence, a pseudofossil
That’d be my vote, although I note that some actual fossils do look much like that, including fossil jellyfish (yes, really) and coprolites (fossilized poop). Or Gastroliths (“stomach stones”)
But I’d put my money on Concretion. They’re far more common than jellyfish or coproplites
Missouri or Illinois. I have had it so long I don’t recall where I found it. I camp a lot in both states.
Given the density your numbers suggest (>4g/cc) that has to have a fair amount of metal - it is much denser than most rocks
What were the other rocks like in the area where you found this - did this one stand out as very different?
Also, does a magnet stick to it at all?
I have a similar rock that was found in Ohio and was part of a Native American relicts collection that was at a farm auction. It showed a lot of human usage as if it were used in some unknown capacity by owner. There were huge clamshell, arrowheads and pendants along with it. Many knowledgeable people were there but could only speculate what it was used for. I even showed it to one of the officers of the Ohio Archaeological Society and she was stumped as to what it was used for, but that it definitely used.
So I took it to shows of fossils, rocks and Native American artifacts for years and it was a great conversation piece but no resolve to what it was. Until finally I found a geologist at a show who claimed to know what it was. He said that although it was not magnetic it was an iron nodule, which is also called a concretion.
Isn’t it likely that the concavity is the result of a smaller, harder stone spinning around in place for eons, driven by a flow of water?
There can be a range of things that cause depressions in a stone - a gas bubble formed when it was molten, your abrading rock suggestion, a softer rock insert or patch eroding out faster. Given it is a pretty dense rock, my best guess is a bubble, but I’d not rule out your suggestion either.
I will try to get some close ups.
No, a magnet does not stick to it at all.
Thanks for the info so far. I did send pictures to Washington University Geology Dept. (I’m in St Louis) Maybe they will get back to me.
I honestly don’t remember where I got it, I was a late teen/early adult. Possibly down in the Ozark National Scenic Riverways. I spend a lot of time down there canoeing.
And some rocks are just weirdly shaped from the get-go. Flint/chert nodules, for example, are often knobbly, and sometimes those ‘knobbles’ are in the negative form of cavities and holes - just as a result of the way the rock formed (similar to a bubble I guess, but flint/chert is not igneous).
Given the density of 4g/cc and the dark aspect of surface, it “may” be a meteorite.
But I bet on marcassite: heavy (4 - 5g/cc), non magnetic, found in sedimentary rocks. Does it sparkle when you rub flint on it?
The high density of some meteorites is because of the iron content, and the OP has said that it isn’t magnetic. Not a meteorite.
Definitely not a meteorite. The vesicles in the first picture (at about 1") are a dead giveaway.
If I had to guess, given that it is not magnetic and has an appreciable density, I would guess a chunk of water-tumbled hematite. Not too uncommon, and occasionally sold as meteorites to the unsuspecting.
Again, it’s just a guess.
Hematite is a good suggestion. If you try dragging your rock across a mildly abrasive surface - like the unglazed back of a ceramic tile (or some smooth-ish concrete), hematite will leave a reddish-brown mark
Definitely not marcasite, that always has a distinct lustre when polished and usually an obvious crystalline habit.
Could be haematite or a haematite-rich ironstone. Not what I’d expect to find in the Ozark Riverways area, which looks to be a karst terrain, but common enough in the Midwest as a whole.
