Found this cool rock at lake Tahoe. It has 2 white rings around it that are so perfect I thought at first they were drawn. Now it lives in my Chia pet garden. Here’s an additional pic.

Found this cool rock at lake Tahoe. It has 2 white rings around it that are so perfect I thought at first they were drawn. Now it lives in my Chia pet garden. Here’s an additional pic.

Oh I get it. It’s just funny that the smoothing would stop perfectly right there.
If it’s not rings that would have to be it. OP, you have an industrial CT machine to check, right? /s
Edit: Also, it’s basalt?
just guessing on the darker part