This rock pack is based on the weathered rock (https://www.blendswap.com/blends/view/60436) - ported to Cycles and added some variations. I also re-textured it a bit (I added an overlay texture) and included in the file are some similar materials that can be used with the rock model.
Nice work! Thank you for sharing! I'll credit you when I use it.
some beautiful rocks, well shaped!