Mystery rock picked up in an area with Jeffersonville Limestone Devonian Period fossils. When I picked up the rock I assumed it was the inside of brachiopod. The inner part has a blue appearance. It reminds me of some of the crinoid stems found at Lake Cumberland, Kentucky. At one time, I thought it might be agate but there are no layer lines. Could it be some sort of blue opaque quartz or blue chalcedony? Then there is the crystal area, that I guess is calcite.
The area surrounding the nodule shape has a lot of dendrite patterns. I did not test the rest of the stone but I assume it is limestone. Found in Clark County, Indiana. I only found one half, not sure where the other part is.
What the nodule looks like from the back.