Can anyone tell us what this ‘rock’ actually is? I found it around here last month and have been curious ever since. Because I had time on my hands, I took pictures with my Coolpix and made a web page (from my old domain). I explain everything there and have some cool pics of this groovy stone object. Any info would be appreciated, because I have not studied much geology (unfortunately).
It’s pretty clearly not a fossil- the close-ups make it look like the interior is a lot of small quartz crystals stuck together. I would suggest that it is a section of geode- you have a crusty outside and a quartz inside which is covered in little pits containing nodules of other minerals. (The little pits, then, are formed by bubbles of gas, if I remember my geology classes well enough.) The shape is also suggestive of some sort of geode-like pipe. I’m afraid I don’t know the geology of your area well enough to know how plausible this explanation is, but based on purely visual inspection you seem to have a chunk of quartz crystal formed by igneous processes, and containing small pockets of other minerals.
Could be, as it looks very quartz-like to me, and we have literally tons of quartz littered across the countryside around here. But all of it I’ve seen is not cell structure quartz or if so, larger blocks. Nothing like this. But could be something like that.
The ammonite suggestion was more along the lines of what I initially thought. Some sort of fossil remains of an ancient sea creature.
The area where it was found is crawling with snail/shell fossils, some the size of baseballs or larger. Huge, heavy things. We got a lot of them as well, but there were hundreds. They are obvious shell fossils, not like this item.
The area is on a hill and obviously seen lots of erosion. You can kick up Native American arrowheads and pottery if you stay a few minutes. The hill is quite high and near a creek. I can only imagine that they used it as a look-out post. There is worked flint everywhere.
I got sidetracked there… It’s just amazing to pick up a piece of history sitting right on top of the soil.
He’s very probably correct, at least partly, but that doesn’t mean it can’t also be a fossil.
Neither one rules the other out.
I have found many fossils that had crystals formed inside. Geodes are not uncommon at all. They are found in many different rock formations, igneous and sedimentary.
My money is still on ammonite, with a bonus crystaline formation included.
I think what we are looking at is pretty clearly a piece of sedimentary rock. My reasoning? Looks like ripples in clay and sand that you will see on the bottom of a shallow pond. The interior, I’ll bet is just larger pieces of sediment.
On the other hand, you should ignore me, because even though rocks fascinate me, I don’t know squat.
As far as I can see there is nothing “ammonite” about that. The inside curvature looks smooth enough to have been cut or drilled. Possibly like when large formations and hillsides are drilled into and explosive charges placed in to “clear out” the way. It doesn’t taste salty does it?
My guesses would be gypsum as mentioned by yabob, possibly igneous quartz, or quartzite (metamorphosed sandstone, where you can sometimes still see the shape of the sand grains). To make a more accurate guess, I’d have to have the thing in my hand. Your best bet is to find a museum or university nearby and ask a geologist to take a look at it, because it’s awfully difficult to tell from a picture what it is.
I’d guess that it’s somebody’s art project. The natural rocks in the area contain lots of fossils but if it doesn’t, it’s probably not native material. The two curves look very circular, and the wavy face contrasts highly with the rough outide flat area. It’s tough for me to imagine anything natural that would have had such different effects on surfaces so close to each other their edges touch. The two pics [crater.mpg] and [upclose.mpg] look very much like some Georgia white/gray marble I have laying around, if it’s ground flat and polished a bit. There are toothed chisels made just for creating the “spines” on the curved outer surface. Also, in most beginning scultpure classes the instructors encourage you to do abstract designs -beginners tend to attempt to duplicate masterpieces in miniature and end up with nothing but a pile of gravel. - MC
Thanks to all who have taken a shot at this! I appreciate the info. I did take some more shots of some interesting lines from the sides (the outer ‘shell’ of the rock). These are not the large lines that are obvious in most of the other shots. They are very thin, evenly spaced, and appear even crosshatched. Even more, they appear to go perpendicular to the large lines on the side of the whole thing (in comparison to them, not on them).
I added a thumbnail of each and a picture that shows the region that contains the close-up of the lines. I thought they were interesting. Maybe it will help you out.