This is a heavy specimen, perhaps a casting. Found on the shorelines of the Raritan River, along the beach of Johnson Park in Highland Park, NJ.... two days after the washout of Hurricane Sandy.
If the photos seem incomplete, vied the photos at their offsite upload link.
There is a small break in the specimen, revealing what seems to be most likely quartzite inside. The outer surface is quite smooth and microscopically pitted. The petina is dark stained and pieces of rock and pebble are stuck inside the formation, unremovable.
I have consulted multiple reputed people in paleontology, minerology and geology. Special trips to Professors at Princeton, Kean and Rutgers were futile... even after lab microscopes and spectrometers were used..... And My latest trip this weekend was to the World Gem/Fossil/Mineral Expo in Raritan Center, Edison, NJ. Not a single person had a similar answer to just what this could be. Please help, and perhaps guide me to the next person who might know definitely what it is. What I can say.... is that I wish I had a photo of the faces of each person that looked at this for the first time in their hands.....