How 'hard' are sandstone & granite relative to each other? How do each respond to extreme cold & retain cold?

While they can be equal in hardness one would normally find that the granite, being of igneous origins, is more chemically bonded and therefore more difficult to break apart. However, the individual minerals within the granite may be harder or softer than the sandstone which is usually composed of quartz which has a hardness of 7. If the sandstone is porous, it will not take extreme cold well at all as any moisture inside the pores will freeze and thereby facture the rock.The granite doesn't have this problem.