Nahcolite is a soft, colourless or white carbonate mineral with the composition of sodium bicarbonate (NaHCO3) also called thermokalite.

[4] Nahcolite was first described in 1928 for an occurrence in a lava tunnel at Mount Vesuvius, Italy.

[5] It occurs as a hot spring and saline lake precipitate or efflorescence; in differentiated alkalic massifs; in fluid inclusions as a daughter mineral phase and in evaporite deposits.

[2][4] It occurs in association with trona, thermonatrite, thenardite, halite, gaylussite, burkeite, northupite and borax.

[3] It has been reported in a Roman conduit at Stufe de Nerone, Campi Flegrei, near Naples; in the United States from Searles Lake, San Bernardino County, California; in the Green River Formation, Colorado and Utah; in the Tincalayu deposit, Salar del Hombre Muerto, Salta Province, Argentina; on Mt.