Definition of petrograph in English:
petrograph
noun ˈpɛtrə(ʊ)ɡrɑːfˈpɛtrə(ʊ)ɡraf
A carving, especially writing, upon a rock; a rock inscription.
Origin
Early 19th century; earliest use found in Robert Southey (1774–1843), poet and reviewer. From petro- + -graph.