Coprolite? Coral? I don't know what this is

[Caroboneferous]

I found this on a sandbar along the Kansas River in Shawnee, KS.    I found a collection of aquatic fossils on the sandbar that look like they had been washed up.   I don't know what this is, it appears to have small bone or cartilage fragments imbedded in it (I'll take some close up pictures and upload them if needed).    The top face has irregular divots while the back side is more smooth.     The whole piece is hard and heavy (best I can tell, it's has a 7 or so on the hardness scale).  

I haven't really seen anything like this before.   

[fifbrindacier]

@GeschWhat?

[Thomas.Dodson]

This just looks like worn calcareous rock to me, possibly highly replaced with silica. The inclusions you see could be chert or shell material but we would need better pictures to guess.

[Rockwood]

It might even be volcanic tufa. It's a little tough to tell in a photo.

[Caroboneferous]

It does seem to have fragments of something in it, possibly a shell fragment, I’ve attached a picture.   The fragment looks like a fingernail cutting and reflects the light.

there’s also these fibrous strings that cut through, they look like thread, but are as hard as the sample. 

We don’t really have any volcanic rock here, this could be limestone that had pieces eroded away.  It’s interesting.

[Rockwood]

5 minutes ago, Caroboneferous said:

We don’t really have any volcanic rock here, this could be limestone that had pieces eroded away

Limestone will react (bubble) with vinegar. You might crush a small bit to get a clearer result.

[GeschWhat]

Looking at the closeup photos, the composition doesn't really look like what I would expect to see in a coprolite. Good news is that Kansas coprolites will usually stick if you touch them to the tip of your tongue, so that is a good way to rule out coprolite. I'm getting more of calcareous vibe.