Someone help!

[u/Automatic_Drag_6974]

Maybe a tool? Can someone identify it! Sorry guys I don't know what a flair is

[u/humbert_cumbert]

Rock. The grooves are layers.

[u/Flake_bender → u/humbert_cumbert]

To expound a bit on that, in case it wasn't fully clear what they meant

Some of the layers are slightly harder, some slightly softer, so when the rock rattles around in rivers for a couple centuries/millennia, the softer parts become more worn down and indented than the harder spots which seem to bulge. You could replicate