How borax is mined
California's great borate pit is 230 meters deep, and its ore gets dissolved completely so clean crystals can regrow.
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The short version
Borax comes out of a dead lake. In California's Mojave Desert, crews drill and blast a huge pit in the Kramer deposit and truck the ore to crushers. The plant then dissolves the borates in hot liquor, lets clay settle, and cools the liquid until clean crystals grow. Those are filtered, dried and shipped as borax pentahydrate, borax decahydrate or boric acid.
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Blast the old lakebed
Drills bore holes for explosives that loosen both the overburden and the ore. Large shovels scoop the broken rock into 220-ton haul trucks. The Boron pit measures 3.2 km long and up to 230 m deep.
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Crush to one inch
Surface crushers break the trucked rock to about one inch, and a conveyor carries it to the processing plant.
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Dissolve in hot liquor
Crushed ore meets hot liquor and the borates go into solution. Screens catch the insoluble rock and sand that refuse to dissolve.
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Settle out the clay
Saturated solution flows into thickener tanks, where heavy clay sinks to the bottom and clear liquor passes on.
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Grow and dry crystals
Crystallizers cool the liquor until borate crystals form. The slurry is poured over fabric filters to shed water, and rotating dryers finish the damp crystals before they ride a belt to storage and shipping.
Worth repeating
- Borax was first found in dry lake beds in Tibet, and native tincal was traded along the Silk Road to Arabia by the 8th century AD.
- Melted borax dissolves many metal oxides, and the result is a glass.
- The lake behind California's Boron deposit existed about 16 million years ago, fed by hot springs carrying sodium and boron.
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Sources
Cite this page: "How borax is mined." Assembly Line, 2026-11-03. https://assemblyline.org/make/borax