Rock coatings can be used to constrain the rate of abrasion by wind on Mars. The susceptibility to abrasion for potential rock coatings on Mars (salt/salt-cemented coatings, rock varnish, and amorphous silica) were determined experimentally. Rock coatings generally abrade more easily than the host rock, although amorphous silica is an exception. If coatings exist on rocks at the Mars Pathfinder landing site, then the rate of abrasion is extremely low, consistent with previous studies of erosion rates. Alternatively, rock varnish or silica coatings could protect the rocks from sandblasting, although this may require coating formation under current to recent conditions. The Pathfinder area may lack efficient abrasive particles, and the observed duneforms may be composed of sand-size dust aggregates rather than crystalline particles. ¿ 2000 American Geophysical Union