rocks which serve as the initial raw material in the production of mineral fertilizers. The term “agronomic ores” was introduced in 1921 by la. V. Samoilov and applies to ores containing phosphorus, potassium, and nitrogen. Ores containing phosphorus are represented by the apatites and phosphorites. The largest apatite deposit is found in the Khibiny Mountains (Kola Peninsula). Phosphoritic deposits of the stratified type are known in Kazakhstan (in the Kara-Tau Range); of the nodular type, in the European part of the USSR (the Egor’evsk, Viatka-Kama, Shchigry, and other deposits). Potassium agronomic ores are mined at deposits of potassium salts, among the largest of which are the Verkhnekamskoe (Perm’ Oblast), the Starobin (Byelorussia), and the Stebnikovo (Carpathian region). Nitrogen is a component of sodium and potassium nitrate, which are found much more rarely in natural mineral formations. Other agronomic ores are carbonate rocks (chalk, limestone, or dolomite), serpentinites, sapropelites, bentonite, perlite, vermiculite, and peat. For the preparation of trace-element fertilizers, the ores of copper, boron, manganese, zinc, cobalt, and molybdenum—as well as waste products of sulfuric acid production (pyrite cinders)—are used.