Honed marble is a tough, durable surface, but it's also porous, making for an easily etched surface if the wrong food or chemical should spill onto it. In addition, when not protected by a coat of finish, marble is susceptible to scratching. These small scratches can gather particles of dirt within them. The dirt in turn can cause the scratches to expand in length or depth, increasing the damage. In order to repair the marble, you'll need to remove the scratches completely. After removal, polishing the marble will restore the original honed finish. A matte finish is slightly less wet-looking than the shiny finish common to other marble types.
Clean the surface of the marble using a clean cloth and cleanser formulated for marble use. Rinse with water and allow the marble to dry before continuing.
Attach 100-grit sandpaper to an orbital sander. Start the sander and sand down the edges of any scratch in the marble surface until there is no noticeable ridge along the scratched edge. Use small circles along the length of the scratch to prevent creating furrows in the marble. The scratch should appear as a light line in the marble. Run your finger over the line to ensure no rough sections remain.
Switch the sandpaper on the sander to 150-grit. Run the sander along the scratch to grind the scratch down completely, blending it into the surrounding marble until it's no longer visible.
Change to a 220-grit sandpaper and go over the sanded area, smoothing the marble surface. Run your finger over the surface after smoothing to make sure that you can no longer feel any trace of the scratch. Remove any slight etching in the marble caused by acidic substances using 220-grit sandpaper as well.
Pour a quarter-sized dollop of polish on the marble. Mix the polish with water until you create a slurry with the consistency of cake batter. Attach a polishing pad to a 4-inch angle grinder. Turn on the grinder and apply the pad to the marble surface to spread the polish over both the formerly scratched area as well as the immediately surrounding area. Turn off the grinder and remove it from the marble. Use a sponge dipped in clean water to clear away the slurry.
Turn the grinder back on and reapply the polishing pad to the dried polish on the marble. Buff the marble by moving the pad over the polish in small circles until you achieve a matte finish, in which the surface barely shines without appearing wet. Repeat the process if necessary until you reach a finish that matches the undamaged marble surface around the scratched area.
Apply a layer of stone sealant to the marble using a foam applicator to keep the marble from staining. Wait 48 hours to allow the sealant to dry before using the surface.