This effect was generated in Filter Forge, a Photoshop plugin that allows you to create your own filters.
This is a pixelation filter that uses two overlapping "stones" noise components to create the pixelation effect. Although fairly simple, some nice effects can be created by varying the inputs. Try the presets on, for example, a landscape.
pixelate pixelation fragments stones noise
This filter has earned its author one of our rewards. They are given to the authors of popular filters and include a free copy of Filter Forge.