Marbles, serpentines, and onyxes are traditionally prized for their aesthetic appeal, accentuated by distinct veining and often bold colors. They are relatively softer than granite, although some serpentines are as dense as some granites. Marbles can be scratched by kitchen utensils so it is best to use cutting boards and other protective measures. Use only non-abrasive products when cleaning marble. Marbles can also be etched by chemical attack. These stones are calcium carbonate based and are damaged by exposure to acidic solutions such as lemon juice, tomatoes, vinegar, etc. The use of inappropriate cleaning agents may also trigger acidic attack. Acidic solutions can permanently etch the surface of the material. The application of a sealer will reduce, but not eliminate, the vulnerability to acidic attack. Honing or removing the polished finish from marble will make the surface easier to maintain when used as a kitchen counter.