No offense but it's probably nothing special imho. Just a water worn rock. Probably igneous or metamorphic in nature. If you want a.specific indentification, you have to at least knock off a good sized chip and post a photo here.
Hi All, My parents have a rock (maybe it is something else?) My Dad found it over 50 years ago in Maryland in the edge of the water of the northeast river in the Chesapeake. They recently took it to a local college and the geology professors didn't know what it was. One of them said she thought it was thousands of years old and that it was formed before the river would have been there.. I'm very interested in finding out what it is, as it has been a mystery all of my life. Also...when you shake it, something rattles inside of it. And it is very heavy for it's size. My Mom used it for a doorstop for many years. That is a quarter in the pic