These are a bit of an experiment, using Luke's APS Modelling Compound to create basic outcrops on top of a lump of un-modeled cheap polystyrene.
Then as the piece was drying working into the surface with tools to get the rock feeling and then a wire brush to help with some of the markings. This piece is about the size of two fists pushed together, so it would make a decent outcrop on its own.
Finally after about half an hour when the compound had dried I gave it a wash with some brown and then a top wash of black. Will be using this method to see what else I can use the technique for shortly.