I picked this rock up in one of the eastern Louisville, Kentucky road cuts that has Ordovician Period fossils. Originally, I was attracted to a conical shaped cephalopod mold looking rock. Once I picked it up, it had a small exposed area of a trilobite thorax. The ridges of the thorax had matrix in them so it seemed like a good idea to sand blast them clean.
I took it to my cousin and pointed out that a cephalon was partially visible and maybe a whole trilobite was there. So he sandblasted the rock for about 20 minutes and what a surprise. There were sections of three Flexicalymene trilobites there. The largest one is about 2 cm long.
This is a work in progress. More matrix needs to be removed to see if another cephalon exists. Notice the white marks on the rock made by the engraver tool.