Which is harder, marble or granite?

Granite is much harder than marble. The hardness of stone is measured on a scale of 1 to 10. Ten is the hardest mineral. Diamond is a ten. Most marbles fall in the 3-5 range and granites fall into the 7-8 range.

A simple test to determine if you are dealing with marble or granite is to try to scratch the surface of the stone with a knife blade. A knife blade has a hardness of about 6. If the surface scratches you are dealing with a marble or limestone. If its difficult to scratch you may be dealing with a granite.