halite - display specimen of pale pink halite crystals from Searles Lake, California
This halite crystallized under the salt surface in one section of Searles Lake. The pale pink color is due to salt-loving (halophylic) rod-shaped bacteria that produce a red carotenoid pigment similar to that found in tomatoes and red peppers. This is a fugitive color, and will fade under sunlight or fluorescent lighting. In the very saline northern arm of the Great Salt Lake, a salt-loving algal species, Dunaliella, produces the red color seen there. As shown here, the specimens are upside down from their position in nature. These crystals hung down into the brine pool below the dry salt surface and are particularly dramatic.
Searles Lake has been mined for borate minerals since 1876 and is partitioned into a number of evaporating ponds. One of those ponds produced halite crystal specimens in the fall of 2016. Today, Searles Valley Minerals produces borax, anhydrous borax, boric acid, anhydrous sodium sulfate, sodium chloride, and soda ash (sodium carbonate) from the brines pumped from evaporating ponds and from wells drilled into the over 900 feet of evaporites and muds that fill the Searles Basin below the salt playa surface. That dry surface is ephemeral, and has been flooded during exceptionally wet years. The salt deposits formed with evaporation of glacial meltwaters at the end of the Pleistocene, as the climate dried out and warmed. A similar deposit was mined in Death Valley, where from 1893-1899, 20-mule-team wagons brought borax to the railroad at Mojave, California, a ten-day one-way trip.
Halite specimens can absorb water in a humid climate, and are best displayed in an air conditioned room or in a plexiglass display case containing a desiccant similar to that which comes with electronic equipment. A quick rinse under a cold water tap is generally safe if the specimen gets dusty, but quick means quick! Specimens are somewhat fragile when wet, as the mass is held together by dry salt, but once dry they become stable. We have specimens collected over 20 years ago that are still attractive, as they were kept in a display cabinet in an arid area.
The Basin and Range province is a collection of NW trending ranges with salt lakes, occasionally wet but usually dry, in the intervening valley bottoms. Since drainage is interior, with no outlets to the sea, the salt that would have ended up there was concentrated in the valleys as the climate dried at the end of the Ice Age. Think of the Great Salt Lake and Lake Bonneville in Utah as examples.
Photos here show tourists examining the salt crust at the bottom of Death Valley and the trace of the fault that caused the magnitude 7.1 July 5, 2019 earthquake crossing the salt pan of China Lake, near Ridgecrest, California, one valley and mountain range west of Searles Lake, where this halite was collected. That earthquake has interrupted the annual collecting day allowed by Searles Valley Minerals each October.
The pencil is 5 1/2" long, for scale.
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