Marble is a relatively soft stone. On a measurement of hardness (MOHS), marble is approximately a three out of ten. Marble is made of calcium, just like your teeth. If you eat something to hard you will break your tooth. If you eat a lot of sugar you will get a cavity. Stone reacts the same way. If an improper chemical is applied to the surface, corrosion will begin to form cavities in the stone.
Listed below is the famous Measurement of Hardness (MOH) Scale for stone. This is a guide developed in the 1800's which helps evaluate the strengths and weaknesses of the stone being used. For example, softer stones would require the use of a less active chemical and a more frequent dust mopping program.