In 1862 while prospecting for gold and silver in the Slate Range Mountains, John Searles’ engineer complained that soda from the salt pan to the west contained enough borax to interfere with its proper influence in refining ore. John also learned that borax was being mined north of San Francisco and that it was quite valuable - $1 per pound. That summer he prepared samples and with his brother Dennis visited the borax mining company. After an initial show of interest, the borax executives said their samples contained not a trace of borax and that to get rich they should look for copper. Much later, in mid January of 1873, a man passed through the Searles brother’s gold mining camp, now at Soledad, with a sample of borax from Teel’s Marsh in Nevada. When John saw that sample he knew that 9 years earlier he had in truth made borax from the muddy crust on the salt pan west of the Slate Range. He quickly formed a company with three partners and entered the borax mining business at what is now known as Searles Dry Lake.
The vast mineral resource in Searles Dry Lake is the result of unique geological forces. These included raising of the Sierra Nevada Range, nearly a million years of volcanic activity and intermittent glaciation. Glacial ice ground the mountains into fine powders easily leached by glacial melt-water and volcanic hot springs brought other soluble minerals to the surface. Together these mineral-laden waters flowed through a chain of lakes where sand and mud settled leaving only mineralized water to enter Searles Valley. Between glacial events, intense desert heat evaporated all the water and the dissolved minerals crystallized, leaving Searles Lake as it exists today with its 16 saline mineral layers separated by layers of mud. The last glaciation followed by drying ended about 10,000 years ago. Today the deposit contains 4 billion tons of soluble mineral salts and extends to a depth of about 350 feet.
Brine from these salt layers is today's source of sodium, potassium, borate, carbonate, and sulfate that are processed in facilities that trace their lineage back to John W. Searles’ San Bernardino Borax Mining Company. From a modest production of a few tons of borax per month in 1873, shipments from Searles Valley today total more than 1.7 million tons per year, serving a wide variety of industrial and agricultural needs. In addition, more than 120 million kilowatt-hours of electricity are sold to Southern California Edison
Today, the Argus Plant produces soda ash (sodium carbonate) and bio-carb (sodium bicarbonate) using a process based on carbonation of lake brines. The Westend Plant refrigerates a mixture of carbonated brine from the Argus Plant and lake brine to produce sodium sulfate and primary borax that it either refines into pentahydrate borax or transports to the Trona Plant. The Trona Plant refines primary borax from the Westend Plant into refined decahydrate borax and anhydrous borax and also uses a solvent extraction and evaporation process to produce boric acid. Salt (sodium chloride) is produced on the lake using a solar evaporation process. The Argus Utilities Plant produces steam and electricity, mostly for use in the plants. In addition to the mineral extraction operations in Searles Valley, the Company has two subsidiaries -Trona Railway Corporation, a railway used to move coal in and products out, and North American Terminals, Inc. in San Diego, a port facility to facilitate shipping products to customers world wide. The Company’s corporate office is located in Overland Park, Kansas.