Fossil, rock?

[FireDove]

[jpc]

fun rock

 

[Fossildude19]

This looks like some sort of ironstone or sandstone, to me.  Hard to tell from photos.

[FireDove]

It's very hard and heavy I found it in a creek near my home. I thought I could take a saw to it and see if it was rock or metal but didn't want to damage it till I checked with you all.

[digit]

Agreed that it is a suggestively shaped ironstone rock of some sort. If you have a saw that could cut through this rock and you are curious to see what it looks like inside you won't be damaging a fossil. If you do cut this rock open please post some images of the inside surface as we're a bit curious as to what it looks like inside.

 

I see you are finding a bunch of interesting rocks while digging in your yard. Most of the fossils in northern Illinois tend to be quite old (Silurian & Ordovician) so fossils tend to be fairly primitive organisms from hundreds of millions of years ago (glaciers scraped off most of the younger formations so no things like dinosaurs). You might find this map to be of interest. You can use it to see how old the surface rocks are in your area. Once you find the age of the rocks in your area (e.g. Silurian) you can do an internet search to see what types of organisms were around at that time. That will give you a good idea what types of fossils might be possible in your area.

 

https://resources.isgs.illinois.edu/maps/bedrock-geology-map-illinois

 

If you are interested in fossils you might wish to search this forum (and the wider internet) for the search term "Mazon Creek". It is an abundant and interesting group of fossils just about an hour's drive from Chicago.

 

https://en.wikipedia.org/wiki/Mazon_Creek_fossil_beds

 

 

Cheers.

 

-Ken