EXDLicH., ECONOMIC GEOLOGY LIMESTONES, &C. 149 



compact coke. These are piefeirecl for smelting and other processes. 

 In my report on the coal region of Evanstou I shall have occasion to 

 enter into the details of comi^osition and economic utility of these coals 

 more fully than could here be done. 



LIMESTONE. 



On the eastern slope of the Wind Eiver Mountains, in the Sweetwater 

 and Seminole Hills and near Eawlings, lunestones are abundant. At 

 the first-named locaUty the admixture of silica generally renders them 

 uui)nre, but some strata can be found that are comparatively free from 

 it. Within easy reach of the settlements, these beds may at some future 

 time prove serviceable. Excepting the silica, they are sufficiently x)ure 

 and ahnost quite free from alumina. Within the same regions some beds 

 may be found that could be utilized as marble. They occiu' near tlie 

 base of the Carboniferous series. In the Sweetwater and Seminole Hills 

 the limestones show essential^ the same characteristics, but contain, 

 perhaps, less silica. On the eastern slope of Rawlings Peak strata com- 

 jiosed of this material occupy a very prominent position. I am informed 

 that some lime is burned in that vicinity, and that the quality obtained 

 is good. Along the western slope of the range and south of the Sweet- 

 water Hills limestones occur, but they are very impui-e, approaching 

 more closely in character calcareous shales. 



GYPSIBL 



This mineral occurs most abundantly in the lower i)ortion of the Tri- 

 assic beds. Below the junction of Twin Cr^ek and the Little Popo-Agie 

 I noticed the most extensive exposures. Beds were there found reaching 

 a thickness of several feet. Generally this gypsum is light red, gray, or 

 yellow, but white strata can be found. It is crystalline rather than com- 

 pact, resembling alabaster in texture. Some of the beds would furnish 

 excellent material for x)urposes of carved ornamentation. Fibrous gyp- 

 sum (satin-spar) is found together with the other, occurring in narrow 

 seams and veins cutting across the strata. As gypsum is essentially a 

 local deposit, the thickness of the beds varies considerably at different 

 localities. Near the Poi)o-Agie settlements, however, there is an ample 

 supply for all purposes. Throughout the formations composed in a 

 great measui-e of shales we find crystals of selenite. Mostly they are 

 quite small, but they occur in tablets of several inches in thickness and 

 a foot in diameter. Among all others, the Wasatch Grou^) may be re- 

 garded as the one most highly favored in this respect. 



CE]MENT. 



Many of the shales and marls which occur in the Cretaceous and Ter- 

 tiary Groups Avould answer very well for the maiuifactiu'e of ordinary 

 and hydraul'ic cement. Within the Sweetwater Group there are some 

 strata that could be used for these purjjoses with bat slight i)reparatiou. 

 Many of the marls are arenaceous, but if such were selected that are 

 comparatively free from sand they could be utilized. It is not probable 

 that ever any very great demand for cements will arise in that section 

 of country, and the expenses of transportation would most likely prove 

 to be too heavy to reahze profits by shipment. It is Avell, however, to 

 know that the materials are at hand to render the inhabitants independ- 

 ent in the matter of cements, which often may become an important 

 question. 



