I'm going to give my best shot at some CnC but what I say may not apply in blender, i've only experience in 3d Studio Max and a very, very limited knowledge of Maya (no-one knows how to use Maya) so take what I say as advice in a general sense rather than specificall following it as it simply may not be possible
You've got the shapes of the rocks spot on, which is hard in itself because, well, to be perfectly frank, rocks are so random in nature it's difficult to imagine what one would look like as a 'typical rock'. The bump map used is also quite accurate for the use. I cannot fault the rocks in any way other than in the the specular and gloss levels, but I'll get to that in a moment.
My main advice that I can offer with these is that since Gold is probably one of the most non-reactive elements on the planet, it wouldn't blend into the grey of the stone. It'd be solid, as in completely seen in it's shiny glory - though not necessarily in stripes as Jagex would have you believe but in specks, or indeed completely unseen unless you've found gold in some magical semi-transparent rocks.
As with any kind of ores, it would be unlike to find it on the surface of the rock and even more so with the same texture and glossiness (which I'll get to later) as the rock it's found in. Iron ore for example will have a distinctly different texture than the type of rock it's in. As such;
What you can do to improve it is model the gold into the rocks manually, much like Jagex has cut out parts of rocks to create strips of colour, you could do the same and add tiny specks of glittery moneymaking happiness to add extra realism. This will not only allow you to create the illusion that the gold is
in the rocks rather than on them, but give you an easy(ier) way to modify the material maps to provide a look inconsistent with the rocks themselves.
As promised, i'll continue with lighting and specular/gloss levels. Simply stated, you need to alter the values for these until you hit a shininess that corresponds with the objects in the scene. Metal and stone are two very different things and you'll find that if you stick with 3d for long enough, specular and gloss values will make the biggest difference between sand and glass other than of course, reflectivity and diffuse maps. Modelling the gold seperately is the best place to start for this and you can increase and decrease the values until you reach a sort of level that results in what you'd expect to get from a plain, white circle on a black, Photoshop canvas and then using a Gaussian blur. A metallic material needs to look very shiny where the light hits it and almost black where the light doesn't. Grab yourself a can of coke and hold it up to the light. Instantly, you'll see the place where the light hits the can. Emulate this in your scenes.
Stone on the other hand is quite different. I'm lucky in the sense that 3d studio max comes with basic presets for architectural materials like metal and stone and if blender does the same - use them, tweak them, learn them. Stone won't reflect light unless it's polished and in a mine; that's unlikely. The specular and gloss levels will be low, as opposed to high on a metallic material.
Lighting in the scene is good but you need to turn down the intensity of the fill light and/or increase the intensity of the key. If you're using three lights - well done, if you're using two, add a third. You need a back-light..
Other than what I've said there's one last thing you need to add, and it's crucial to a successful render.
Diffuse maps.
Your gold rocks have colour, they have texture, and they have specular lighting. But they don't have 'substance', if that makes sense. They look like rocks, they do, but only in shape and texture. Google image search or even go outside and find a reference sample, photograph it (hi-res) and put it on your computer. Apply the diffuse map, apply a UVW map to scale the diffuse map properly and your rocks will improve tenfold.
(don't go out looking for a reference sample of gold, that'll take ages. Instead find something like steel and alter it on photoshop. I've used my kitchen fridge a couple of times XD)
I hope the CnC wasn't too bad, but it's better than a rating yer?
More CnC = Better?
Remember, reference material is the key!
