Marble is a relatively soft stone.  On the MOH scale, marble is approximately a three out of ten.  Like our teeth, marble is made of calcium, and will break and develop cavities when exposed to incorrect treatment.  If an improper chemical is applied to the surface corrosion will begin to form cavities in the stone. 

We list below the famous MOH Scale for stone.  This is a guide developed in the 1800’s that 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 more frequent dust-mopping program.

MEASUREMENT OF HARDNESS SCALE (MOH)

1. Talc
2. Gypsum
3. Calcite (most marbles)
4. Fluoride
5. Apatite
6. Feldspar (granite)
7. Quartz (granite)
8. Topaz
9. Corondum
10. Diamond

The MOH scale measures the resistance of stone to hardness.  When sediment and grit are harder than the surface, they will scratch and harm the stone.  For example, a piece of hard plastic is about 2.0.  It will not scratch calcite (marble).  However, a grain of sand that measures a 6, will scratch calcite, but will not scratch quartz, which is a granite.  The harder the stone, the more resistant it is to abrasion.  Exterior sediment that is tracked into building usually measures from 3 to 7 on the MOH scale.