...If the pics did not post let me know, I'm new to this site
Huntsman53 got it right. Here is the more-specific ID. The clues are that you described it as a "round" rock, and the characteristics we see in the photo. It is a chert/flint nodule which was hollow when it first formed, but eventually it became filled up "solid" inside with Quartz crystals and some "banded" Chalcedony. (I recognize it because way back in college, I was a rock-hound and Geode-hunter... still got some of those in a box in my attic.)