Sylvite was first discovered in very small crystals in the
volcanic fumaroles of Mt. Vesuvius, Naples Province, Italy. Other important European localities include Muntanya de Sal (Salt Mountain), Cardona, Catalonia, Spain; and the Boulby Mine, Loftus, Yorkshive, England. In Germany, good Sylvite has been found at Wathlingen, Lower Saxony; Stassfurt, Saxony-Anhalt; and at the Hattorf
Potash Works, Werra valley, Hesse.
In the U.S., the two most important deposits of Sylvite are the Carlsbad Potash District, Eddy Co., New Mexico; and Niland, near the Salton Sea, Imperial Co., California. Some of the world's largest deposits of Sylvite are in Canada in the province of Saskatchewan, especially at Esterhazy and Rocanville.