What is this Rock?
Hi! Lovely photos! Thank you for the scale with the rock.
Although you didn't mention where you are located, I suspect you might be near factories or historic factories. Industrial process can create some of the most curious "slag" either through a manufacturing process or if a building burns at a high temperature. The lovely green "rock" looks like remelted glass (silica) with other inclusions. The exterior has a melted bubbly look to it.
It might be fun to do research on the history of your property to see what might have happened there in the past. Great find!!!!
Thank you. I will look into it and see what we find. We are in thornville/ Newark Ohio area and located very near to Indian mounds. They are all around us.