What sort of rock is this?
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Dino poop?

I stepped in something that looked like that one time. Very interesting rock.

Maybe some variant of a Septarian nodule.

Cool rock. Don't know what it is, but I like it.

Maybe a weird geode.

actually yeah sorta i think...looks like chalcedony of some sort.....atleast the striped stuff in this photo should be:

I looks like it could be a slightly darker variety of chalcedony rose or like that. May I ask what specific region or geology formation you found it in?

If you have a rock or mineral show/club near by they could help you id it and perhaps pay you a little cash for it.

prolly not worth much.....neat as hell and i woulda picked it up to but these kinds of quartz rocks are some of the most common semi precious stones to be found....even large ones....unless they are something odd like the Montana Moss Agates we have or some of the various jaspers found around the US(and other countries) they just arent worth anything and even the odd ones usually arent worth that much compared to alot of other semi-precious stones....

Yup. Looks like a geode to me too. They are best once cut and polished. Either just in half or slices. If you are careful, they can be cut thin enough to transmit light through them.

A lot of really nice images of geodes HERE.

Cool pictures. Thanks for the link!

Picked it up hunting near Heppner Oregon. It was laying on top of the ground in a grassy meadow near camp. Someone may have picked it up somewhere else and forgot to take it home.

Looks knappable....:D

at the very least the striped stuff in the pic i copied would be....not 100% sure of the rest, i assume its likely largely the same stuff but i dont know without having my hands on it...



as you prolly know Oregon has a hell of a volcanic history and how it likely formed is in a hollow in a lava flow that filled with silica rich ground water and later the softer volcanic rock eroded away leaving the harder silicon dioxide....

If you want to you could find a really smooth solid stone, like one from a creek bed and gently hammer off some of the cortex surrounding the formation and get a better pitch what's in there. It looks like you might have a pretty decent knife blade in there!

You could have saved a lot of typing and just said "hydrothermal precipitation".

and how many here would have understood it....me you and maybe a handful more

In college a friend picked up a geode at some tourist trap during a road trip. Somehow I convinced the cival engineering dept to let me use their diamond saw to cut the geode in half. Unfortunatley it wasn't one of the hollow geodes, but still pretty neat to see that mass of crystals on the inside.

Yes, a geode or more locally known as a thunder egg.

That doesn't look like a geode to me. Most geodes, or at least the ones I've seen, are more symmetrically round and have quartz deposits insides. That looks like some type of volcanic deposit. The yellow looks a lot like sulfur.
That thing in the center looks somewhat like striped agate. It almost looks like something that just got bonded to the other deposit but not formed with it.

Upon looking again, it could be broken segment of some type of cave formation like a stalagmite or stalagtite. That would explain the striped formation in the center(layers) and a lot of cave limestone formations have some pretty vivid colors due to other elements being deposited.

geode is a rough term....if its what i think it is then yeah technically its a geode, just not one of the nice looking ones with the perfect hollow center....all a geode is, is a hollow in volcanic or sedimentary rock that gets filled with minerals from hydrothermal action, and the above looks like it fits that description....

Funny, I cut my finger when I picked it up!