This is a very-large block (cabinet or display specimen) of the fossil coral Foerstephyllum Vacuum. This coral is over 400,000,000 million years old from the Upper Ordovician period. It was recovered from deposits in Bardstown Kentucky (Shelby County, Laurel Dolomite).
This piece shows the coral pattern clearly and would make a fine display example or it could be used as rough for lapidary work - parts of it should take a nice polish when cut.
Refer to the photos. The brass cube measures one square centimeter and is shown for scale. You are purchasing the coral specimen shown. It weighs approx. 5.21 kilograms (or about 11.5 pounds). It measures approx. 10 inches by 6 inches by 3 inches. Your purchase will include an ID label.