Tequesquite
Tequesquite or tequexquite (from Nahuatl tequixquitl) is a natural mineral salt containing compounds of sodium chloride, sodium carbonate, and sodium sulphate, used in Mexico since pre-Hispanic times mainly as a food seasoning. It is found naturally in central Mexico particularly in previously lacustrine environments where the mineral salt forms a sedimentary crust.
Sometimes it is confused with Potassium nitrate, but its chemical composition is completely different.