Any ideas

[Rosco53]

I was at the Rockford Fossil Prairie a few years ago and while goin through my finds again found these amongst them. Grabbed them that day just because they were odd, wondering if anyone may have an idea what they are?

First, same piece. Maybe cent sized?


Then this one. The one piece fell out:


Found with devonian fossil shells, if that helps. No idea as to the layers etc, bit new to the rock/mineral thing. Thanks in advance!

 

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[BridgetownTreasures]

Gems embedded in the stone are garnets. Hard to tell if the one that fell out is another garnet - is the metallic bit gold in color, or is that just a reflection?

 

[fuss]

I think it more likely Sphalerite with pyrite and or marcasite especially for that area. But the one pic with the white surface the minerals do look like like garnet crystals but I think its probably a Sphalerite cluster.

 

[Moesia]

What is the color of the streak?

 

[DDancer]

Not so sure about Sphalerite considering where you found it, that and the from of the crystals. My thought is that you have Pyrite thats in transition to becoming Limonite considering the shape of the structure and on that bits that have fresh surfaces showing. Again I'm also considering where you found it~ the age of the deposite would support my thoughts on it as pyrites and psuedomorphs of it occur in that type of setting. Sphalerite occurs in ore's and where you found it would be sedimentary type deposits. Here's a link on what the psuedomorph will look like : https://www.mindat.org/gm/2402