What is the difference between hard water and etch marks and how can I tell?
Hard water is a high amount of mineral deposits like lime, silica or calcium that are left behind when the water dries. These are typically found around the base of faucets, showers handles, shower walls, etc. If you scrape the surface with your nail and get a white powdery residue, that is probably hard water. Removing this problem stone is an easier process, but extreme care must be taken to not scratch or etch the stone.
Etching is an entirely different issue. Etching the result of stone becoming damaged as a result of the stone being exposed to an acidic liquid (orange juice, wine, some dishwashing rinses, vinegar, etc.) that actually “eats” into the calcium of the stone. The only fix to an ecth mark is to mechanically hone (refinish) the stone. The honing process smooths the stone so the light can reflect back as evenly as the surrounding areas that were not etched. This process is best performed by a stone craftsman as improper honing can furtehr damage teh stone.