Rock Salt / Halite Crust

Physical Properties

Hardness: 2-2.5 on Mohs scale; Color: Colorless to white, often tinted yellow, brown, or red by impurities; Luster: Vitreous (glassy); Crystal Structure: Isometric (cubic crystals ubiquitous, though often massive or crust-like); Cleavage: Perfect cubic; Specific Gravity: 2.16.

Formation & Geological History

Formed through the evaporation of saline lake or sea water in arid climates. These evaporite deposits occur in sedimentary basins and can range from recent formations to hundreds of millions of years old (e.g., Permian age deposits).

Uses & Applications

Primary source of table salt and road de-icing salt. Used in the chemical industry for producing chlorine and sodium hydroxide. In construction, it is used for soil stabilization. High-clarity crystals are used for specialized optical components.

Geological Facts

Halite is essential to human life; historical 'salt roads' were vital trade routes. Some specimens can contain ancient fluid inclusions—bubbles of water trapped millions of years ago that may even contain dormant bacteria.

Field Identification & Locations

Identify in the field by its distinct salty taste (not recommended if contaminated), its cubic cleavage, and its softness (can be scratched by a fingernail). Commonly found in dry lake beds (playas), salt mines, and as efflorescence on cave walls.

Identified on: 4/28/2026

Mode: Standard