Thomas LavergneHow come those rocks are so neatly sliced? Any rock expert here has a guess?
I saw them (and many more) in a dry river bed in the hills, northern #Italy.
Simon Brooke@lavergnetho they're highly stratified rocks (likely shales and mudstones) which shatter easily on the discontinuities between the strata.
Imagine a river bed that dries out intermittently. While there's water, sediment gradually accumulates and packs itself neatly and densely, under gravity and lubrication. When it dries, the surface gets dusty, and when the next inundation comes the next layer of sediment doesn't adhere so well to the previous one.
@simon_brooke sounds plausible, thanks.