Some natural stones such as marble and limestone are relatively soft and porous, so it is susceptible to etching. Avoid using abrasive materials when cleaning them, or detergents that contain harsh chemicals. Use only mild soap and water applied with a soft cloth to clean marble and limestone surfaces, and dry thoroughly after. Granite is tougher, so you have less problems with it. However, for best results, you should use mild and phosphate-free soap, and one clearly labeled for use on natural stone.