gaylussite, a carbonate mineral, hydrated sodium and calcium carbonate [formulated Na2Ca(CO3)2ยท5H2O], that precipitates from soda lakes. It has been identified in deposits at Lagunillas, Venezuela; in the eastern Gobi (desert), Mongolia; near Ragtown, Nev., U.S.; at Borax Lake, Mono Lake, and Searles Lake, Calif., U.S.; and Independence Rock, Wyo., U.S. Gaylussite readily weathers to calcite. For detailed physical properties, see carbonate mineral (table).