The extent and nature of the varnish cover (i.e., natural patination) within rock engravings are compared with that on adjacent rock surfaces. The implications of these observations for relative dating are discussed. Particular attention is given to the possibility that the extent of varnish cover within engravings may not be indicative of engraving age. The varnish on all engravings is dark grey to black, often shiny and fairly thin. predominant elements: silica, aluminum, iron and manganese; other elements: calcium, potassium, titanium, and sulfur.The chemical content is very variable but can always be described as manganese-rich. -- AATA