What do you mean by rock salt?

Rock salt, also known as Halite in the industry, is a mineral formed from Sodium Chloride (NaCl). It is mostly white in color or can be colorless. Rock salt is also found in some other colors like light blue, dark blue, purple, pink, yellow, or gray totally depending upon the amount and type of impurities it contains.

The salt lies in the beds of Sedimentary evaporite minerals caused by large lakes and seas drying up. These beds may be thick about hundred meters.

Rock salt is basically formed by the evaporation of salty water (like sea water) that contains Na+ and Cl- ions. Rock salt also includes some other salt variations like common salt and table salt. which are required for human life on earth.