https://gamesartist.co.uk/river-pebbles/
Material Artist Alexey Kirsanov has created this realistic River Pebbles Material; in this article he explains the process of creating a realistic material using Substance Designer. It covers references, layers, simulating elements, tiling, blending, rendering and lighting.
https://www.artstation.com/coldtaiga
https://www.artstation.com/artwork/obQz44