Identifying comes with alot of technique, like closer up images that show the different texture; depth/smooth/dry/chipped/stonecrust/direction of modification.
Follow these colourdifferences.
Sequence;
1 standing point
2 second silhouette
3 shades
4 textures
All in combination of the boxgrid.

Like if one changes ones thoughts from a crude lump of stone to a sophisticated work of representation one is halfway there.