Some stones are porous and readily absorb liquids and moisture. Materials like limestone and sandstone are extremely absorbent, whereas granites and serpentine (green marble) are denser, but will still absorb liquids that are allowed to remain in contact with them for extended periods of time. In areas where stains are likely to develop, protective measures should be taken.     
       The use of a sealer will help prevent staining in most situations such as very wet. Even a sealed surface can stain if left in contact with a staining agent for a long period of time. Therefore, all spills should be wiped up as soon as possible, and coasters or napkins should be set when serving food or drinks on a stone bar, table, or counter top. Soft drinks, coffee, tea, and fruit juices contain mild acids and can etch the polished surface of a stone and stain quite rapidly. These should be cleaned off immediately with a mild soap and warm water. Remember - do not use any abrasive cleansers，for it can corrupt the stone.