Flying Saucer flint?

[Charles Jones]

I found this 6” diameter stone in a small branch near a woodland/ Mississippian mound site. There was no other pieces that looked similar. On the relatively flat bottom, in the middle, there is a slick, hard button about 5/8” in diameter. The rest of the surface is a limestone looking rock that is smoother on top and looks like layers on the bottom.
I have heard of flying saucer flint, but have not seen one. Don't feel like breaking it up. Looks too interesting.