Trona also sodium sesquicarbonate dihydrate, Na2CO3•NaHCO3•2H2O. It is mined as the primary source of sodium carbonate in the United States, where it has replaced the ammonia-soda process used in most of the rest of the world for sodium carbonate production. Trona is found at Owens Lake and Searles Lake, California; the Green River Formation of Wyoming and Utah. The trona near Green River, Wyoming, is the largest known deposit in the world and lies in layered evaporite deposits from 240 to 490 m below ground. Trona has also been mined for nearly 100 years.