English: (public exhibit signage at the Columbus Rock & Mineral Show)

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Rock salt, also known as "halitite", is a crystalline-textured, chemical sedimentary rock composed of the mineral halite (NaCl - sodium chloride). Rock salt is an evaporite - it forms by the evaporation of water (usually seawater) and the precipitation of dissolved minerals. Other evaporites include rock gypsum (gyprock), rock anhydrite, and rock sylvite (sylvitite).

Rock salt has economic significance - it is mined as a source of salt for the food industry and as a de-icing agent.

Shown above is a map of Ohio depicting areas where salt or rock salt is produced. Vast underground salt mines are present in northeastern Ohio, in the Cleveland area. Some extend under Lake Erie itself.

Ohio rock salt occurs in the Silurian-aged Salina Group. Silurian-aged evaporites also occur elsewhere in the Great Lakes area of America. Other significant, large, and famous rock salt occurrences include the subsurface of the Gulf of Mexico and the Salt Range of Pakistan.

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From exhibit signage:

Solution Mining Water softener salt is produced by a method called solution mining. 1) Water is pumped into a natural ground salt cavity. 2) Then the pure salt solution is pumped out. 3) The salt solution is partially evaporated.

4) The moist salt is put into presses or molds where evaporation is completed.