Many deserts contain large salt flats. Minerals like sodium chloride (table salt) are dissolved in rain or ground water . Water quickly evaporates in the dry desert air and the salt is left behind.
Wind carries salt dust from the ocean to the desert. Salt also comes from ancient sea floors that may be buried far below the ground surface.
Activity — grow your own salt crystals:
Would you have guessed that roses grow in the desert? Powdered gypsum is dissolved in rain or groundwater then crystallizes inside sand dunes. The new gypsum crystals look like the petals of a rose.