structural:summarization
Mining

Trona, also known as trisodium hydrogendicarbonate dihydrate (Na HCO CO ·2H O), is mined in several areas of the US and provides nearly all the US consumption of sodium carbonate. Large natural deposits found in 1938, such as the one near Green River, Wyoming, have made mining more economical than industrial production in North America. There are important reserves of trona in Turkey; two million tons of soda ash have been extracted from the reserves near Ankara.