What is this?

[Sherri.S]

Greetings!  I'm new on here. This came from my Father who was a rock hound and traveled to Colorado every year.

I inherited this and have no idea what it is. Can anyone help? (3 lbs 4 oz, 4 1/2" x 4 1/2".) Thank You! Sherri

[Fossildude19]

Welcome to the Forum, Sherri.   

 

What you have there is a very cool looking concretion.     

While many people confuse concretions with eggs, there are a number of things that point to this being a concretion. 

No definite eggshell texture. Layers too thick.  Concentric layers of matrix (Classic indicator of concretions).

 

 

Have a look through our Egg Guide. 

 

 

Any idea where in Colorado it came from? 

 

[Sherri.S]

Thank you Tim. I'm guessing from Colorado because my dad was a fossil hunter and spent every fall there throughout the 50's and 60's. He left me some of his collection with no explanation so I am only guessing. I'll have to read up on "concretions".  Here's another angle. I love looking at it - it makes a beautiful and interesting paper weight on my desk! :-)

[Fossildude19]

Sherri, 

 

It is definitely a super cool piece. 

It looks like some sort of chert or agate nodule, in your second picture.

Here it is with the reddish tint removed:

 

   

[Sherri.S]

Sorry Tim, I didn't answer your question. Where in Colorado I have no idea. He was an Engineer who worked for the State Board of Health and worked with water pollution all over Kansas. Now that I think about it - it might be from Kansas? After I learn a little more about concretions maybe that's possible? He had a quite a rock collection that he found or dug up around the old coal mines too. 

[grandpa]

Hello Sherri S.  My eldest daughter's name is Sherri.  Welcome to TFF from Austin, Texas.  FossilDude has you off to a great start, I think.  I would maybe add one thing.  From the second photo, I get the sense that the outer layer might be pyrite, the surface looks "brassy" to me.  You can check to see if I'm on to something by doing a "scratch test".  Rub the metallic looking surface across the rough surface of the back of your porcelain toilet lid.  If it leaves a greenish to brownish black streak, you might likely have a pyrite nodule/concretion.  Let us know what the results of this test are.

And again, Welcome!

[Sherri.S]

Thank you Grandpa! Sherri with an "i" doesn't seem to be that common. I did your scratch test and it didn't leave a streak - it didn't scratch the surface at all. So that was interesting.  I'm going to include a picture from another angle - the bottom is completely different. For some reason I wasn't able to upload more than one picture at a time. 

[grandpa]

Interesting, I'm not sure where to go from here.  It's a unique looking rock for sure. 

[Sherri.S]

I had to chuckle at that because when you look at the bottom it does look entirely different. Thank you for your observations. Much appreciated.