The possible relative dating of petroglyphs by nuclear measurements on desert varnish is explored. The abundances of 30 major and trace elements in desert varnish samples from the Grimes Point petroglyph site in western Nevada were measured by neutron activation analysis techniques. Samples of both desert varnish and heart rock from a non-artifactual test boulder of andesite were studied and the elements tungsten, arsenic, antimony, thorium, uranium, manganese and cerium exhibited the greatest enrichments in the surface samples and may be of use for dating purposes.