Thanks for the reply! Very nice pics, also. I forgot to mention in the post that the outside layer is agate. For a better description of the stuff on the inside, it’s a mass of little balls, and the ones that are broken in half are what look like the crinoid stems.

I have a saw to cut this in half for a better look, but I want to gain a better understanding of it in case cutting it up would devalue it.

Thanks again :)