It depends on how close you want to zoom in on this, but have a look at this: https://cgcookie.com/tutorial/realistic-particle-dirt-in-blender
Salt has a crystalline structure that should be a lot easier to model than dirt, but the techniques he uses should help you to get an idea of how to do this.
Rigid bodies are probably overkill and Scatter Object is not meant for this kind of ‘heaps’…
