690 



UNITED STATES MINERAL RESOURCES 



now utilized in about 90 percent of the petroleum 

 catalytic cracking installations and have greatly 

 increased the recovery of gasoline. Natural zeolites, 

 however, have found only limited use in this country. 

 Clinoptilolite is used to remove cesium from radio- 

 active wastes (Brown, 1962), and chabazite is used 

 to desiccate mildly acidic natural gas. Zeolitic tuff 

 has been used as a pozzolan in cement. 



In Japan, on the other hand, zeolites have been 

 extensively mined and utilized since their discovery 

 there in sedimentary deposits in 1949. Clinoptilolite 

 and mordenite are the only zeolites currently mined 

 in Japan, and they are utilized chiefly in the fields 

 of agriculture and animal husbandry. Minato and 

 Utada (1969) described the following uses: Desic- 

 cant for gases, separator of oxygen from air, adsorb- 

 ent for obnoxious odors in farm yards, filler and 

 whitening agent for paper, and a soil conditioner to 

 increase the efi'ectiveness of chemical fertilizers. 

 More clinoptilolite is mined in Japan for the last 

 use listed than for any of the others. 



Some of the natural zeolites may find applications 

 in pollution control. For example, laboratory and 

 pilot-plant studies by Pacific Northwest Laboratory, 

 Battelle Memorial Institute, Richland, Wash. (Mer- 

 cer and others, 1970), indicate that clinoptilolite is 

 effective in the removal of ammonia from waste- 

 Vi^ater. Also, recent studies suggest that mordenite 

 may be suitable for the removal of SO2 from stack 

 gases. 



The United States is self-sufficient with respect 

 to the present fledgling zeolite industry. Because of 

 the large potential zeolite resources and the diverse 

 zeolite mineralogy, the United States will not only 

 remain self-sufficient when new markets develop but 

 will probably become a major exporter. 



EXPLOITATION 



Production figures have not been published for 

 natural zeolites in the United States ; however, small 

 tonnages were mined from upper Cenozoic tuffs. 

 Several hundred tons of chabazite, clinoptilolite, and 

 erionite have been mined each year since the mid- 

 1960's; the mined deposits are near Bowie, Ariz., 

 near Hector, Calif., and in Jersey Valley, Nev., re- 

 spectively. 



Exploration and sampling of bedded zeolite de- 

 posits by commercial organizations have been active 

 since the late 1950's in Arizona, California, Nevada, 

 Oregon, Texas, and Wyoming. The exploration 

 peaked in the early 1960's, when the search con- 

 centrated on natural molecular-sieve zeolites that 

 might compete with the synthetic zeolites. Since 

 1970, exploration has accelerated again. This time 



the emphasis is on the location of zeolite deposits 

 suitable for pollution-control processes. 



Japan is probably the world's leading producer of 

 natural zeolites. Since the mid-1960's, Japan has had 

 an annual production of about 100,000 tons. About 

 half of this production is from one mine, at Itaya, 

 Honshu. Clinoptilolite and mordenite are the only 

 zeolites currently mined in Japan. 



GEOLOGIC ENVIRONMENT 



Zeolites have been known since the mid-1750's, 

 and they occur in rocks that are diverse in age, 

 lithology, and geologic setting. Zeolites have been 

 recognized in sedimentary deposits since 1891, when 

 Murray and Renard (1891) described phillipsite in 

 deep-sea deposits. Prior to the early 1950's, however, 

 most zeolite occurrences were reported from frac- 

 tured fillings and vesicle fillings in igneous rocks, 

 particularly in basaltic rocks. Most of the large 

 attractive zeolite specimens in museum collections 

 were obtained from igneous rocks. In recent years, 

 zeolites have been recognized as important rock- 

 forming constituents in low-grade metamorphic 

 rocks and in a variety of sedimentary rocks (Hay, 

 1966). The zeolites in sedimentary rocks are very 

 finely crystalline and do not appeal to mineral col- 

 lectors; however, deposits of this type are volumi- 

 nous and have great economic potential. The re- 

 mainder of this chapter summarizes those zeolite 

 resources in sedimentary deposits. 



Of the more than 400 published reports that de- 

 scribe zeolites in sedimentary rocks throughout the 

 world, more than 75 percent were published in the 

 last dozen years. The factors chiefly responsible for 

 this recent surge of reports are (1) the widespread 

 use of X-ray powder diffraction techniques in the 

 study of fine-grained sedimentary rocks, (2) the 

 exploration for zeolite deposits suitable for com- 

 mercial use, and (3) the early review papers by 

 Coombs, Ellis, Fyfe, and Taylor (1959) and Def- 

 feyes (1959), both of which emphasized the wide- 

 spread and relatively common occurrences of dia- 

 genetic or authigenic zeolites in sedimentary rocks. 



Zeolites are among the most common authigenic 

 silicate minerals that occur in sedimentary rocks, 

 and they have formed in sedimentary rocks of di- 

 verse lithology, age, and depositional environment. 

 Those zeolites given in table 148 have been reported 

 from sedimentary rocks ; however, some, such as 

 faujasite, gismondine, gonnardite, scolecite, and 

 thomsonite, generally occur in trace amounts and are 

 rarely reported. Only nine zeolites commonly make 

 up the major part of zeolitic rocks. These are anal- 

 cime, chabazite, clinoptilolite, erionite, ferriei'ite. 



