Ammonite? Geode? Help!

[Frak425]

Hello!

So my sons, ages 7 and 5, were hiking with me near the Hoosier National Forest near Bloomington, Indiana and stumbled upon this specimen. I know nothing about fossils but thought the spiral looked to perfect to be a rock. I stumbled across this forum and thought I'd throw it out there.

We had been looking for geodes and this thing rattled, so I decided to cut it in half (2 symmetric sides) and sure enough, it's beautiful! It's also rather large, approximately 7 inches in diameter.

But we have no idea what it is.

Thanks for any information you might share. My kids and I are just so curious as to what we have found!!

[Frak425]

Also, I realize there's a fairly good chance that this is nothing special. But if anyone could point me in the direction of how to clean it up and polish it I'd greatly appreciate it. My kids have just had a blast with this thing.

[Raggedy Man]

Definitely a geode and a nice one at that. My wife and I go to the Keokuk, Iowa area every year and bring back 4 to 5 5 gallon buckets full of geodes ranging from golf ball size to basketball sized. It's a blast

Best regards,

Paul

[Triceratops]

Cool find!

[Ludwigia]

The form certainly looks deceptively like it could be an ammonite, but on seeing the sliced insides, I would have to agree with Paul in saying that it is not, since there are no tell-tale signs of what one would expect to see inside, like shell, septa, siphuncle and the like. It is however a beautiful find with the quarz druses and the exceptional form. Please show us a photo once you've polished it up.

[abyssunder]

Nice geode.

[Frak425]

Thanks for the responses!

I know I didn't post photos of both sides of the exterior, but they are symmetrical. I mean the spiral pattern matches on both sides.

If it's just a geode I'm happy because it is beautiful. I just don't understand how that shape could have happened naturally from what little I understand about geode formation.

[John K]

I'd like to suggest that it is a fossil (maybe a large gastropod?) that has weathered out as a cast and replaced with quartz in it's present-day geode form?

something like this, only on a larger, fuller scale:

it's very cool!

[howard_l]

I would say it is a coiled nautiloid, geodized nautiloids are fairly common around Brooks KY just south of Louisville. If the area you are looking at in Indiana is Mississippian then it could be also. This one looks a little more geodized which usually destroys or explains the original fossil to the point it isn't recognizable but this one looks like it is showing the inner whorls.

[Bev]

I'm no expert, but I also agree that it is a fossil - either gastropod or cephalopod but I'm not familiar with that area.

Personally, I have found several cephalopods that are geodized on the inside - truly stunning finds!

And yours is Drusy quartz! I LOVE Drusy quartz! It is even now considered a gem stone in jewelry circles.

I would be THRILLED to find this! And you even had a saw to cut it!

The exterior looks like limestone. I would think that would be hard to polish. However if it is "shedding" sand, what I do to mine is coat them with Modge Podge as it is water soluble - no fossil harmed. The Drusy quartz is stunning and can be cleaned with a tooth brush and a bit of baking soda then rinse thoroughly - sit on a window sill so that it can sparkle!

CONGRATULATIONS on a Great Find!

[Ludwigia]

I would say it is a coiled nautiloid, geodized nautiloids are fairly common around Brooks KY just south of Louisville. If the area you are looking at in Indiana is Mississippian then it could be also. This one looks a little more geodized which usually destroys or explains the original fossil to the point it isn't recognizable but this one looks like it is showing the inner whorls.

I'm no expert, but I also agree that it is a fossil - either gastropod or cephalopod but I'm not familiar with that area.

Personally, I have found several cephalopods that are geodized on the inside - truly stunning finds!

And yours is Drusy quartz! I LOVE Drusy quartz! It is even now considered a gem stone in jewelry circles.

I would be THRILLED to find this! And you even had a saw to cut it!

The exterior looks like limestone. I would think that would be hard to polish. However if it is "shedding" sand, what I do to mine is coat them with Modge Podge as it is water soluble - no fossil harmed. The Drusy quartz is stunning and can be cleaned with a tooth brush and a bit of baking soda then rinse thoroughly - sit on a window sill so that it can sparkle!

CONGRATULATIONS on a Great Find!

Well, you guys seem to have had some concrete experience there, so I would agree with you that it's within the realm of possibility that it could have originally been a fossil. Back to square one.

[Frak425]

Thank you all for the input. I'll be sure to post some updated photos once I've got them cleaned and polished. Pretty cool find for someone who had never really looked at rocks before. Makes me want to go out and keep searching!!