Salt is normally associated as very useful for cleansing as it has purifying energies. Cyrstals on the other hand are very different, each crystal has its own unique energy. they are very diverse and if used correctly can be very powerful. When I purchase a new crystal I use salt to purify it of negative energies before charging with my own energies. I'm sure that salt crystals can be used for something but no way can it be a substitute for the real things. Do some reading up on crystals and you will see what I mean.
Blessed Be :-)