SULFUR 



615 



resource. The preceding calculations were re- 

 stricted to the petroleum in the conterminous 

 United States, inasmuch as petroleum under the 

 continental shelves and in Alaska is so low in 

 sulfur that a resource in such oil should not 

 be postulated. 



4. Of the 100 million tons of sulfur contained in 

 the identiiied resource of pyrite, 10 million tons 

 arbitrarily is assigned to the recoverable frac- 

 tion, and the balance, to the subeconomic re- 

 sources. The President's Materials Policy Com- 

 mission (1952) considered that some 30 million 

 tons of sulfur, contained as pyritic gangue in 

 base-metal ores, constitutes a resource. Al- 

 though much of that pyrite will be rejected 

 with tailings in nonrecoverable form, it is 

 judged that 20 million tons of this sulfur even- 

 tually could be recovered, and this amount is 

 included with the submarginal resources of 

 pyrite deposits shown in table 126. Another 40 

 million tons may occur in extensions of known 

 districts and in areas as yet unexplored. 



5. The 30 million tons of subeconomic resources of 

 sulfur in volcanic rocks cited for many years is 

 probably still a reasonable estimate. Hypotheti- 

 cal and speculative resources are judged to be 

 very small. 



6. Resources of sulfur contained in sulfide ores 

 of base metals are calculated from estimates 

 presented in other chapters of this volume. A 

 nominal recoverable resource of 20 million tons 

 is predicated on recovery efforts prior to pres- 

 ent statutory requirements for cleaner air. 

 Much of the subeconomic identified resources, 

 some 80 million tons, will be recovered regard- 

 less of cost because of antipollution regulations. 



7. Gypsum resources are nearly 50 billion tons, 

 the sulfur content of which constitutes an 

 identified resource of about 7 billion tons, and 

 a hypothetical resource of nearly 2 billion tons. 

 Of this amount, 150 million tons of very pure 

 gypsum has been blocked out as raw material 

 for sulfur production. At present this consti- 

 tutes a paramarginal resource. Huge anhydrite 

 resources, many times greater than gypsum 

 resources, are not included in the accompanying 

 tabulation. 



8. Tar sands are said to contain an identified sub- 

 marginal resource of 10 million tons of sulfur. 



9. The aggregate tonnage of sulfur contained in 

 coal is enormous. Resources of all classes are 

 estimated to be 41 billion tons, but none is re- 

 coverable at present prices of sulfur. In table 

 126, the hypothetical sulfur resource in coal is 



predicated on undiscovered coal lying at less 

 than 6,000 feet depth. 

 10. Shales rich in organic matter, eventually ex- 

 ploitable as sources of liquid or gaseous hydro- 

 carbons, contain at least 1 billion tons of sulfur 

 in the oil shale of the northern Rocky Moun- 

 tains, and 80 billion tons in the black shales of 

 Devonian and Mississippian age in the Eastern 

 and Central United States. The entire resource 

 is subeconomic; no attempt is made here to 

 differentiate between identified and hypothetical 

 resources. 



Recovery of sulfur from resources depends upon 

 the state of the technology, upon the cost of extrac- 

 tion, and now also upon statutory requirements lim- 

 iting sulfur emissions into the atmosphere. The 

 resource data already presented must thus be quali- 

 fied as follows: 



Frasch mining recovers 75-92 percent of the sul- 

 fur contained in the ground, depending on the tech- 

 nological efficiency of the operating companies and 

 on the geological characteristics of given ore bodies. 

 Recovery of sulfur from natural gas exceeds 95 

 percent of the contained hydrogen sulfide, but only 

 about 80 percent of the natural gas is recoverable 

 from the ground. Recovery of sulfur from petroleum 

 has been averaging 15-20 percent, and less than 

 half the petroleum in the ground is recoverable un- 

 der current technology. Recovery of the sulfur con- 

 tained in pyrites is relatively high and that of sulfur 

 in volcanic deposits reasonably high, both probably 

 greater than 75 percent. Recovery of the sulfur 

 contained in base-metal ores has been relatively low 

 in the past, but should increase markedly in the 

 coming years. Experience in the extraction of sulfur 

 from gypsum, tar sands, and oil shale is yet too 

 limited to indicate how efficient recovery will be. 



Little sulfur is recovered from petroleum in the 

 United States. The low sulfur content of most U.S. 

 oils has made extraction of sulfur during petroleum 

 refining seem neither necessary nor economically 

 important. The same is true with other deposits of 

 hydrocarbons and with low-sulfur coal. About 30 

 percent of the bituminous coal of the United States 

 contains less than 1 percent sulfur. 



CANADA AND MEXICO 



Canada and Mexico are among the leading pro- 

 ducers of elemental sulfur. Canada recovers the 

 element from hydrogen sulfide in natural gas and 

 Mexico from caprock deposits. The sulfur in Cana- 

 dian natural gas is an indicated resource of 140 



