A general term for minerals deposited as sedimentary layers by the evaporation of water. Examples are gypsum, anhydrite, and rock salt or halite.
They may be markers of areas of commercial interest, because some evaporites are both non-porous and resilient (they deform rather than break), so hydrocarbon deposits are effectively capped by them.
Since salt water is heavier than fresh water, evaporation from a salt sea causes the salts to precipitate to the bottom.
Study of salts and carbonates in martian rocks deposited on Earth as meteorites, and which appear to be evaporites, may reveal the history of aqueous activity on the surface of Mars.
Useful diagrams at www.geo.msu.edu/geo333/evaporite.html
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