rock salt

Noun

rock salt (countable and uncountable, plural rock salts)

1. The mineral halite.
   • Farther to the southward, the rivers which are affluent to the Colorado, such as the Rio Virgen, and Gila river, near their mouths, are impregnated with salt by the cliffs of rock salt between which they pass.1845, J[ohn] C[harles] Frémont, Report of the Exploring Expedition to the Rocky Mountains in the Year 1842, and to Oregon and North California in the Years 1843-’44, Washington: Gales and Seaton...
2. Coarsely ground common salt, often used as road salt, as feedstock, or for other applications.
3. (Philippines) Synonym of sea salt, due to its rocky texture.

   Synonyms:

   sea salt, due to its rocky texture