Sylvite - KCl.

"Potash" refers to a group of water-soluble salts that contain the element potassium, usually chloride of potassium. It can also be potassium sulfate, potassium-magnesium sulfate, and potassium nitrate.

Potassium, like phosphorus, is an essential element for animal and plant nutrition. Potassium chloride is the major potassium salt mined worldwide. Canada is the world's largest producer; Russia, Germany, Belarus, and Israel are major producing countries. Most output is from conventional underground mines. Israel and Jordan have solar evaporation production from the waters of the Dead Sea. The United States produces potash from brines, which is water that is saltier than seawater; solution mining in Michigan and Utah; underground mines; and the water of the Great Salt Lake. About 80% of U.S. consumption is supplied by imports; Canada is the major supplier of imported potash. About 80% of U.S, potash is used in fertilizer; the remainder is used in medicine and by the chemical industry. It is used to produce decorative color effects on brass, bronze, and nickel.