Searles Lake

History · Geology

About Searles Lake

Searles Lake, in the Mojave Desert, California, is one of the world’s most chemically complex evaporite deposits and the type locality for hanksite. The dry lake bed has been mined since 1873 for its rich Na-K-Cl-SO₄-CO₃-B₄O₇ brine chemistry.

Geology

The lake is a Pleistocene-Holocene playa hosted in a closed basin with hydrothermal Na-K-B-rich groundwater input. Multiple cycles of evaporative concentration produced layered evaporite deposits up to 21 m thick of crystalline soluble salts.

Notable Minerals

Hanksite (the locality’s namesake hexagonal Na-K sulfate-carbonate-chloride crystals — gem-clear hexagonal prisms to 30 cm), sylvite, halite, borax, trona, anhydrite, colemanite, ulexite. Hanksite is essentially restricted to this deposit and a few smaller California analogues.

Collector Notes

Hanksite crystals from the annual Searles Lake “Gem-O-Rama” excavation events are the species’ iconic specimens. Care: most are highly water-soluble and must be stored in low-humidity environments.