606 



UNITED STATES MINERAL RESOURCES 



reserves and resources are irregularly distributed; 

 the commodity, therefore, moves in large tonnages 

 in international trade (Ambrose, 1965 ; Lewis, 1970 ; 

 Lundy, 1949; and Fogarty and Mollison, 1960). 



In approximate order of increasing cost of mining 

 or recovery, the following raw materials provide 

 most of the world's sulfur and sulfuric acid supply : 



1. Elemental sulfur deposits in evaporite rocks. 



2. Hydrogen sulfide contained in sour natural 



gas. 



3. Organic sulfur compounds contained in 



petroleum. 



4. Massive deposits of pyrite. 



5. Elemental sulfur deposits in volcanic rocks. 



6. Ores of metallic sulfide minerals (Cu, Zn, Pb, 



Ni, Mo). 

 Additional large resources of sulfur occur in the fol- 

 lowing minerals or compounds : 



7. Beds of the calcium sulfate minerals, anhy- 



drite and gypsum. 



8. Organic sulfur compounds in tar sands. 



9. Organic sulfur compounds and pyrite in coal 



beds. 



10. Organic sulfur compounds and pyrite in oil 

 shale and shale-rich organic matter. 



Approximately one-quarter each comes from ele- 

 mental sulfur, massive pyrite, and sulfur in oil and 

 gas. Only the elemental deposits in evaporites or in 

 volcanic rocks are mined solely for their contained 

 sulfur. Pyrite deposits can be mined for their sulfur, 

 as the chief product or as coproducts or byproducts 

 from the production of iron and other metals. Sulfur 

 is recoverable from all the other types of deposits 

 only as a byproduct or coproduct that can be used 

 directly in acid manufacture or converted to ele- 

 mental sulfur for shipment elsewhere. Sulfur con- 

 tained in the last seven types of raw materials, how- 

 ever, commonly is lost to the atmosphere either dur- 

 ing processing or through use of the primary 

 product. 



Sulfur and its chemical compounds are used in 

 virtually every segment of the world's industrial and 

 agricultural complexes, as shown by the almost per- 

 fect parallelism between the Federal Reserve Board 

 index of U.S. industrial production and the sulfur 

 demand index (Landsberg and others, 1963). Prin- 

 cipal uses in the United States are in the manufac- 

 ture of soluble fertilizers, synthetic fibers, plastics, 

 papers, pigments, explosives, petroleum products, 

 drugs, and insecticides; sulfur compounds also are 

 used to leach ores and recover metals, vulcanize rub- 

 ber, and condition soils. The physical properties of 

 elemental sulfur, including its low thermal conduc- 



tivity, high strength, and resistance to acids, suggest 

 potential uses as a versatile construction material 

 (Vroom, 1971). Sulfur should be applied to soils in 

 far greater quantities in many parts of the world to 

 balance chronic sulfur deficiencies. 



Sulfuric acid can be replaced by other common 

 acids in many processes, but its low price makes 

 large-scale substitution unlikely. 



The United States has an adequate reserve of low- 

 cost sulfur minerals and compounds and large to 

 great resources of moderate- to high-cost sulfur- 

 bearing compounds. In recent years, production, at 

 about 9 million long tons, has exceeded consumption, 

 the balance accumulating in producers stocks. Since 

 World War II, the amount of sulfur rescovered from 

 natural gas and petroleum has been increasing 

 steadily, and present efforts to maintain cleaner air 

 will result in even greater recovery of sulfur from 

 all sources. 



EXPLOITATION 



It is anticipated that U.S. consumption of sulfur 

 will grow at a rate of 4-5 percent per year, reaching 

 perhaps 30 million tons annually by the year 2000, 

 or about three times the present rate (Hazleton, 

 1970; Lewis, 1970). 



The earliest demand for sulfur in the United 

 States was met by imports of pyrite for acid manu- 

 facture and of Sicilian sulfur for nonacid uses. 

 Shortly after 1900, Frasch mining of caprock sulfur 

 deposits became commercially successful ; and in the 

 following years, plants also were constructed to 

 recover sulfuric acid from pyrite deposits and base- 

 metal ores. The United States became self-sufficient 

 in sulfur supply during World War I. Between World 

 War I and World War II, most domestic sulfuric- 

 acid plants were converted to use elemental sulfur 

 as primary feed. Following World War II, sulfur 

 was recovered in increasingly larger amounts from 

 sour natural gas and from petroleum. Currently, 

 base-metals smelters are installing units to recover 

 larger amounts of sulfuric acid from flue gases. (See 

 figs. 67 and 68.) 



The United States was the major exporter of ele- 

 mental sulfur to the free world from World War I 

 until the 1950's, when new sources were developed 

 elsewhere: caprock deposits in Mexico (1954), ele- 

 mental sulfur recovered from sour natural gas in 

 France (1958) and in Canada (1960), and sulfur 

 deposits in evaporites in Poland (1968). Since 1960, 

 sulfur or sulfuric acid has been recovered in increas- 

 ing amounts from new units in oil refineries in all 

 parts of the world. The United States consequently 

 lost its position as the sole exporter of elemental 



