How trona is mined
Under a Wyoming interstate, one mine's tunnels add up to more roadway than the city of San Francisco has.
- stations
- 4
- things downstream
- 177
The short version
Trona lies in thick beds far beneath Wyoming, left by ancient lakes. Machines bore rooms through the seam and leave pillars to hold up the roof. Belts carry the ore miles to a shaft, skips hoist it to the surface, and crushers reduce it to half-inch pieces for a plant that turns them into soda ash.
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Drive the entries
Continuous miners cut rectangular entries 18 feet wide to open up new ground, leaving standard pillars of 80 by 120 feet. The seam at one Green River mine sits about 1,500 feet down and runs 9 to 12 feet thick.
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Bore the rooms
Twin-rotor borer miners take about 80% of production at that mine, chewing oval, smooth-walled rooms about 8 feet high at 30 inches a minute. A flexible conveyor train follows each machine around curves and breaks up lumps.
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Belt and hoist it
A main belt system in 12 segments runs the ore 13 miles to an underground storage bunker at the shaft. From there it rides 22-ton skips to the surface.
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Crush to half an inch
A horizontal shaft impactor and then a roll sizer reduce the ore to under 0.5 inch. It then heads to the calciner, the first step of the soda ash plant.
minus 0.5 in.
Worth repeating
- Most countries make sodium carbonate by the Solvay process, but in the United States mined trona is the primary source.
- The name trona came to English from Swedish or Spanish and traces back through Arabic to the Greek word for natron.
- Room-and-pillar mining of Wyoming trona recovers an average 55% of the bed, against 30% for solution mining.
Where it goes next
Trona feeds 2 lines directly and reaches 177 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How trona is mined." Assembly Line, 2026-11-03. https://assemblyline.org/make/trona