abstract appearance background coloring colors colouring colours contours contrast contrasts cracks fissures flaws gorge layered layers levels light lines natural pool ravine reflections rock rock-face rockface rocks rocky rough rugged shade shadows shape shapes steep stone stones strata stratum sunlight sunny sunshine surfaces texture textured textures walls water barrier constructed fitted fitting historic large local-stone old patchwork perspectives random randomly-coursed rural secure security shaped sharp solid stone-walled stonework strength strong surface uneven variations variety wall brown colored coloured conglomerate grit gritty veins wallpaper mica silicate