What's this then?

[ewx]

Comments

[atreic.livejournal.com]

My brain is saying sand, but I think it'll be more interesting than that...

[ewx.livejournal.com]

There are more pics on flickr if you click on the image, though where the line between “useful hint” and “making it obvious” is I’m not sure...

[ronebofh.livejournal.com]

I still don't know.

[pseudomonas.livejournal.com]

I'm thinking sandstone (or possibly some other sedimentary rock like mudstone). I can't work out if the horizontal lines are layers as in sandstones or streaks as in cement applied with a trowel.