Here is an image of a polished Prismatophyllum rugose coral fossil (Petosky Stone). It existed in the Devonian Period (410-360 million years ago). The fossil is on display at the 2nd floor (next to of the MSD Tunnel project exhibit) Kentucky Science Center - Louisville Kentucky USA.
Learn more about the Kentucky Science Center (aka Louisville Science Center) at their web site:
https://kysciencecenter.org/
