Abstract

Trona, an evaporite mineral of the compound sodium sesquicarbonate (Na₂CO₃•NaHCO₃•2H₂O), was precipitated in a restricted lacustrine environment during deposition of the Eocene Wilkins Peak Member of the Green River Formation in southwestern Wyoming. Textural variations of the 25 bedded trona deposits are suggestive of multiple depositional scenarios.

Composed of 70% sodium carbonate, trona is referred to as natural soda ash, and refined soda ash is the major industrial product. Over 90% of the United States soda ash is refined by the five Wyoming trona producers. This equates of over 28% of the world's soda ash production or 9 million metric tonnes of the 32 million metric tonnes produced worldwide. The total resource of the trona deposits is estimated an 122 billion metric tonnes. Of this, 36 billion metric tonnes of economical trona reserves are mineable by current technology: conventional "hard rock" methods, mechanized extraction (drum-miner, boring machines), and hydraulically supported longwall shearing.