Ahh right - I didnt know about Cycles. It is a stochasic ray pathing algorithm and it does generate noisy results unless you whack up the number of samples taken to a high degree. No wonder your lighting model is superb ! It really does make for a tremendously realistic result tho - esp with HDR lighting. If you look at the thumbnail, then being downsampled, it loses that noise. So in effect, if you can stand the wait, then render it 4x width and height, then take the result, blur it and resample it back down and it ought to be a whole lot better. Of course it will take forever to render...

Still looks to me tho that those light flecks in the shadowed regions could not possibly be correct so I think blenders cycles has a math bug in it somewhere. I understand why it would be noisy anyway but I think its artificially high noise due to that. If you have bump mapping turned on by using bitmapped textures (like some concrete etc) then make sure the noise frequency is not so high (i.e. tiny bumps) that it would generate weird normals at the ray-surface intersection that would throw the light rays all over the place. If some of the rays are landing into the non shadowed zones then that could be a reason why its generating those flecks and not be a math issue. In effect, what you would be doing is asking for the rock face to be made out of a micro crytalline like surface and those are all the micro glints. I dont know if that is what you have set up and you probably have a handle on the issue. But my tuppence worth of guess there. I have had similar issues with renders in the past with that.