This was either found in Northern Lake Michigan or Southern Lake Superior. We are thinking it is some kind of Agate. What is your thoughts. Thanks for looking.
Looks to me like some sort of sedimentary rock...note the layering. An agate is simply mostly clear chalcedony quartz, with inclusions. Chalcedony quartz is made up of micro crystals, compared to regular quartz. That makes it slightly heavier, and harder.
Jim