Searles Lake

Searles Lake

Searles Lake playa bounded by the Argus and Slate Mountains
Location Searles Valley,
Mojave Desert
San Bernardino County, California
Coordinates 35°45′35″N 117°20′07″W / 35.7598°N 117.3353°W / 35.7598; -117.3353Coordinates: 35°45′35″N 117°20′07″W / 35.7598°N 117.3353°W / 35.7598; -117.3353
Type Endorheic basin
Primary outflows Terminal (evaporation)
Basin countries United States
Max. length 19 km (12 mi)
Max. width 13 km (8.1 mi)
Shore length1 50 km (31 mi)
Surface elevation 493 m (1,617 ft)
Settlements Trona, California
References U.S. Geological Survey Geographic Names Information System: Searles Lake
1 Shore length is not a well-defined measure.

Searles Lake is an endorheic dry lake in the Searles Valley of the Mojave Desert, in northwestern San Bernardino County, California.

The mining community of Trona is on its western shore. The evaporite basin is approximately 19 km (12 mi) long and 13 km (8.1 mi) at its widest point, yielding 1.7 million tons annually of industrial minerals within the basin to the Searles Valley Minerals mining operations. Searles Lake is bounded by the Argus and Slate Mountains.

Geology

Trona, California abuts northwest of the dry Searles Lake bed.
Map showing the system of once-interconnected Pleistocene lakes in eastern California (USGS)

The stratigraphic record at Searles Lake shows that it once held brackish water as deep as 200 m (660 ft). Fluctuations in lake levels correspond to the advances and retreats of glaciers in the Sierra Nevada Range. Thirty major lake levels occurred during the last 150,000 years, represented by a sequence of salt and mud beds. The precipitation of minerals occurred during long periods of lake evaporation.

The lake is home to the Trona Pinnacles, a spectacular geologic tufa formation and a National Natural Landmark.

History

Borax was first produced from the dry lake surface in 1873 by John Searles under the name of the San Bernardino Borax Mining Company. Searles was the first to haul borax using the famous 20 mule team wagons. In 1873, before the railroad was built to Mojave, refined borax was hauled 175 miles by 20 mule teams from Slate Range Playa (now called Searles Lake) to the harbor at San Pedro. The Searles Lake borax discovery has been designated as California Historical Landmark #774, with a plaque at the roadside rest area in Trona.[1] From 1922 to 1928 the Epsom Salts Monorail crossed the Searles Lake on a wooden trestle.

Mineralogy

Hanksite, Na22K(SO4)9(CO3)2Cl, one of the few minerals that is considered a carbonate and a sulfate

Searles Lake is a huge resource of sodium and potassium minerals of the carbonate, sulfate, borate and halide classes of mineralogy. The manufacture of industrial minerals involves a complex solution mining operation in which naturally occurring brines are pumped from wells completed in several salt beds. The brine wells range in depth from near-surface to over 100 meters below the salt pan. A network of production wells, injection wells, solar ponds and piping are used in the production and treatment of the brines.

Industrial minerals are extracted from the brines at the Argus, Trona and Westend plants. Minerals are crystallized from the brines, screened, washed, and dried. The crystals are then baked in rotary kilns to drive off water molecules locked in the crystalline structure. Some recrystallization may be required to achieve a desired composition and granular density. This complex extraction process at the 3 plants is generally referred to as fractional crystallization. It includes the treatment of brines through carbonation extraction, refrigeration extraction and/or solvent extraction. Salt is also harvested from the lake surface and from solar ponds.

Commodities produced by Searles Valley Minerals from their Searles Lake operations include borax, V-Bor (borax with 5 moles of water), anhydrous borax, boric acid, soda ash, salt cake and salt. Mineral reserves exceed 4 billion tons.

Mineral List

Pink halite (rock salt) crystals from Searles Lake. Matrix is minute nahcolite (bicarbonate of soda). Specimen size: 13.5 x 7.7 x 5.2 cm.

Trona Pinnacles

The Trona Pinnacles are in the California Desert National Conservation Area managed by the Bureau of Land Management.

Trona Pinnacles, some as high as 140 ft (43 m), rising from the bed of the Searles Lake basin. Note the white SUV at right for scale.

See also

References

  1. ↑ "California Historical Landmark: San Bernardino County". Office of Historic Preservation. California State Parks. Retrieved 2012-10-12.
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