Yeah, just from the pic it just looks like a rock. However, sometimes you can't tell a lot from one pic. You might try posting it in the North American Indian artifacts forum on here. Very sharp folks on there. Maybe a couple more pics, little closer up, so they can see if it looks like any intentional flaking. Also the context in which it was found is helpful. What made you believe it was an artifact? A known archaeological site maybe, or have you found some points or stone tools there before? All that info is helpful to those guys. Don't be disappointed if it does turn out to be just a rock, keep looking!