The current scales or rock shapes are quite good, but If the monster is meant to be made of rock he needs them over all of its body, without leaving untextured parts: in this sort of creature, untextured flat surfaces can only be interpreted as smooth, thin skin, which isn't rocky at all.
The open belly segments suggests arthropod-like thin shells, which might or might not be the right impression. Does the creature have articulated rigid parts or a flexible but thick skin?
Have you considered using more colours? The light belly is ok, but the darker part of head+horns+legs+back+tail is too uniform.
In nature, turtles have a completely different appearance for back (shell scales), belly (shell plate), head + legs (five very clearly separated parts); you add a tail, which should look different from the nearby back and the legs, and horns, which should be different from the head.
In Pokémon, there is some tradition of bulky creatures with something strange on their back, and their unnatural features are clearly different from the more normal body parts. Example: Bulbasaur, with a large plant in the middle of generic smooth skin.