A study of the mineralogy and hydrochemistry of the Recent evaporite deposit in the Saline Valley playa has been carried out. Halite, thenardite mirabilite, glauberite, gypsum, calcite, dolomite, ulexite, analcime and sepiolite have been identified in efflorescences and/or in sands and muds. Inflow is from springs and mountain streams which disappear on reaching the alluvial fans so that the playa is fed by groundwater flow only. These inflow waters are sodium-calcium sulfate-bicarbonate waters while the playa brines (shallow sub-surface, brine table 0′ to −15′) are sodium sulfate-chloride waters which progressively increase in total ion concentration from the margin in toward the center of the playa. Two initial steps in the development of the playa brines are (1) calcite precipitation within the alluvial fans causing a drastic decrease in Ca 2+ and HCO 3 - proportions in the waters reaching the playa, and (2) precipitation of gypsum at the playa edge, which controls the initial SO 4 2− concentration of the brines. Further evaporation simply leads to waters dominated by chloride and alkalis. The distribution of evaporite minerals in the sands and muds of the playa is zonal. From the periphery to the center of the playa, roughly concentric zones carry gypsum; gypsum + glauberite; glauberite; glauberite + halite. This sequence would be produced in proper order by progressive evaporation under equilibrium conditions of certain solutions in the experimental system CaSO 4-Na 2SO 4-NaCl-H 2O at temperatures between about 10° and 50°C and 1 atm total pressure. Quantitative agreement in composition of experimental and natural brines co-existing with the same assemblages confirms this equilibrium model for the playa evaporites. The model implies that chemical evolution of the natural brines follows a predictable course, one controlled mainly by the bulk composition of the parent water and by the extent of evaporation. The present zonal configuration represents only a stage in the long-range geochemical evolution of the evaporite deposit; outward migration of the existing zones, and addition of a new zone, with time is postulated.