egg shaped object within rock

[matticus408]

Traveling central Iowa and by chance knocked this off the beaten path. Cracked open and inside resides an egg shaped object. The egg shaped object obviously resided within natural stone with crystal and other natural minerals.
Let me know what you think. Let me know if you have questions.

 

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[matticus408]

 

[matticus408]

 

[Cariboo5]

Cool find.......Pays to crack rocks, I have no idea what that is and will be interesting to see what others say..

 

[Jimoutside]

Very nice find, whatever it is!

I don't know for sure what it is, but it reminds me of a hickory nut or walnut or something like that. Fossilized, of course. The kind of pointy end suggests to me it is probably not a bird egg, though I could be wrong.

Are there any lines or other kinds of indentations, stem marks, or anything that might suggest it being a fossilized plant structure, ie fruit, nut, etc.?

 

[stdenis_jd]

you'll need to test the hardness of the nodule, can a piece of glass scratch it (or vice versa, can it scratch glass)?

Looks to me like a chert/flint nodule in limestone. The host rock is definitely limestone, only question is if the nodule qualifies as chert. It looks like it may not have silicified very well which would make it basically a marl/chalk nodule. If it's chalk you'll be able to draw with it on your sidewalk

 

[fuss]

That is really cool.

 

[jeff of pa]

at first Glance, my first thought was spider egg sack.

but That is definitely one for the experts

 

[Jimoutside]

Ancient first generation silly putty, fossilized?

 

[Lygore]

Here in Washington we have a bunch of stones like that that sometimes hold fossilized ocean animals (crabs, shrimp, bones, etc.) they’re concretions. Basically minerals start sticking to the organic matter until it is fully encapsulated and the original animal is replaced with other minerals (agate, jasper, pyrite, opal, etc.). From the looks of the host rock, it appears to be a type of siltstone or mudstone which would also fit.
If you can, try to carefully chip away the nodule until you see something that is either a different color, material, or looks like it might be something. Then try to follow along the item as you remove the rest of the rock.

Another method that you could try, but could potentially destroy the hidden goodies depending on what mineral replaced the organic matter, is to pour liquid drain cleaner and water (50/50 mix or weaker) and see if it dissolves the rock. Vinegar works as well and is safer (weaker). Be sure to wash the whole thing with a baking soda and water paste at first and then leave it in a baking soda and water rinse until it stops bubbling.
I like this as it saves fragile details that may get destroyed when trying to chip or Dremel tool the rock away to expose the item.
Hope this helps!

 

[Eu_citzen]

Could be a concreation.