Trona: Wyoming's Buried Treasure
Beneath southwest Wyoming lies the largest trona deposit on Earth. What is this mineral, how did an ancient lake create it, and why does it matter for both soda ash and hydrogen?
Most people have never heard of trona — yet it’s in the glass of the window you’re near, and Wyoming sits on more of it than anywhere else on the planet.
What is trona?
Trona is sodium sesquicarbonate, Na₃(CO₃)(HCO₃)·2H₂O — a single mineral that carries carbonate, bicarbonate, sodium, and water all at once. It’s monoclinic, typically fibrous to bladed, and ranges from gray-white to a pale honey color. That richer chemistry (compared with plain rock salt) is what makes it both useful and interesting to store hydrogen in.
Trona (sodium sesquicarbonate) is chemically richer than halite — it carries carbonate, bicarbonate and structural water. That extra chemistry makes it far more soluble, which shapes how its caverns are leached and how they behave.
How an ancient lake built it
Trona is an evaporite — a mineral left behind when water evaporates. Tens of millions of years ago, a vast lake (geologists call it Lake Gosiute) repeatedly flooded and dried in a closed basin. Each cycle concentrated the brine until minerals dropped out in sequence, layer upon layer.
A shallow desert lake floods, then evaporates — and as it concentrates, minerals drop out in order: carbonate mud, then trona, then halite. Repeat this for millions of years and you build the thick bedded trona of the Green River Formation. Schematic and illustrative.
Repeat that for ages and you get the Green River Formation: dozens of trona beds, some metres thick, sealed under rock.
Where it is
Tap the basin or a city to learn more. Outline is schematic.
So the buried treasure works twice: a global supply of an everyday industrial mineral, and a potential home for the clean fuel of the future.
Sources & further reading
- U.S. Geological Survey — Mineral Commodity Summaries: Soda Ash.
- Wyoming State Geological Survey — trona and the Green River Formation.
- Trona — mineral data, mindat.org; galleries.com.
The interactive figures are schematic and illustrative.