Blender Cycles+Gimp.
inspiration :
-trailer of The Nature Academy- Rocks scene: https://www.youtube.com/watch?v=vk5C66AFwvs
based on:
-rocks modeling and texturing inspiration:
*Thomas Schlögl: https://vimeo.com/40806926
*CG GEEK: https://www.youtube.com/watch?v=xRDFMYfsIcU
*BlenderGuru: https://www.youtube.com/watch?v=rzXNZkEoTAk
-postprocessing :
*creativeshrimp : http://www.creativeshrimp.com/post-processing-tutorial-in-12-simple-steps.html
Hope you like it!!!