Make colored sand art by stirring a chalk stick in a bowl of salt. it changes the color. Stir less for light color and more for dark richer color. (I used to do this with salt and food coloring. but the chalk stick idea is brilliant!
raised salt painting: create design with glue, cover glue with table salt. Touch watercolor brush on salt, without smearing and watch color be absorbed by salt. Let dry. This looks fantastic. So, inverted rock salt painting.