Here are two tutorials part 1 and part 2 of how to create a procedural stone shape that can be used for procedural placement within substance designer. This is a workflow that I started to work with and later has evolved and became a thing of its own. I have yet to see anyone do this in the community so I wanted to share.
These are some samples of what can be done with making procedural stone shapes in substance designer. Very quick and dirty samples the results can be much much better.