As nouns the difference between lithograph and petrograph

is that lithograph is a printed image produced by lithography; an image produced by etching the image onto a flat surface, then copying the etched surface by applying ink (or the equivalent) to it and pressing another material against it while petrograph is drawing, writing or inscription on stone, as a painting on a cave wall.

As a verb lithograph

is to create a copy of an image through lithography.