carbon stain carbon stain carbon stains are a skin condition characterized by a discoloration of the skin from embedded carbon, usually occurring due to accidents with firearms or firecrackers, or from a puncture wound by a pencil, which may leave a permanent black mark of embedded graphite, easily mistaken for metastatic melanoma.: 47 a carbon stain made from a puncture wound by a pencil (highlighted in circle). carbon stainspecialtydermatology