This is a beautiful fossil coral collected from near Assa Zag, Morocco in the Western Sahara. It's Early Pennsylvanian in age or approximately 320 million years old. The polishing allows for the beautiful, inner structure of the coral colony to be seen. It looks very similar to the fossil coral "petoskey stones" found in Michigan though a slightly different genus of coral.
The genus is Actinocyathus, a type of rugose coral. It had been previously identified as Hexagonaria from the Devonian, though that initial information provided to us appears to be incorrect. A paper on the fossil coral assemblage can be found at the link below:
Mississippian-like rugose corals from a Bashkirian biostrome in the Tindouf Basin, S. Morocco
Assa Zag, Western Sahara, Morocco
Djebel Ouarkziz Formation