Do you mean the ones on the left of this image, next to the cactus? Those are props, although I've forgotten their filenames.
i think thats rock003, but i cant be sure you might have to change the skin number to get that particular texture too just put "rock00" in the model browser to narrow it down to the tf2 rock models
I don't necessarily need those exact rocks. I have seen rocks like that in many places such as around the beginning of PL_Thundermountain (grey) and elsewhere. Thanks for the help.
Those rocks are particularly sneaky. You have to search "cliff" as they are called "cliff", not "rock" as you'd expect. They can be found in the "forest" directory. The other rocks, the desert rocks (which do have grey skins IIRC) can be found in the "mining" directory.