I tried to, it showed how to in the tutorial but I guess I didn't break it up enough, I'll edit it after school tomorrow, or probably in school, we aren't doing anything anymore any who, only 2 days of school left.

First things, are you sure that pallet is the best you could use?
Grey is what stones are like in the realy world, but let's face it, realism isn't what's needed when iconning.
Try a more browny hue, with a touch of yellow, that's what I use when I'm iconning things made out of rock.
Even if you that doesn't work, try dithering the lighter shades, rocks aren't completely smoth, and I think dithering just abit of the highlights can really catch this effect.

And Danny, I just had a big break off school, but I go back on Monday until mid July-ish. D;
And the work I go back to will be twice as hard, probably. : /

Actually, most stones are, atleast what I've encountered. But it does work on the land as well, a cliff NORMALY is grey, if it's litteraly a wall of stones, with a vast drop, but sometimes there are cliffs where the earth has just fallen down, leaving a wall of earth. But if the minerals in the earth are different you can get different effects; for example the grand canyon, the type of rock there is orange, but in most cases, that I've come across they're grey, because the majority of rock is made up of Limestone. And nor did I say "all stones in the world to ever exist are grey,"