Definitely not manos. Those lines don't look like grinding to me either.just my opinion. Is the stone naturally layered all the way through? Or are those marks just on the surface? Kinda looks natural to me.
Can you please pick those two smaller ones at the top, and show a closer photo of both sides? Also; what is that reddish rock under those two in the center?
Can you please pick those two smaller ones at the top, and show a closer photo of both sides? Also; what is that reddish rock under those two in the center?