14 GEOLOGICAL SURVEY OF THE TERRITORIES. 



are exposed from beneath the White River beds and the cretaceous 

 strata, with the usual ferruginous concretionary masses, which have 

 fallen in pieces; and from these latter have fallen out very good speci- 

 mens of Baculites ovatus and Inoceramus. 



Near the sources of the Chugwater are some very rich iron mines, 

 which may prove of great value to the country in the future. The fact 

 of their existence has been known for some years, but no definite 

 knowledge of them has been given to the world. In Stansbury's Report, 

 page 266, there is the following paragraph: "In the bed of the Chug- 

 water, and on the sides of the adjacent hills, were found immense num- 

 bers of rounded black nodules of magnetic iron ore, which seemed of 

 unusual richness." In the winter of 1859-'60, while attached to the 

 exploring expedition of General W. F. Eaynolds, I made a trip to the 

 sources of the Chugwater, and found great numbers of these worn masses 

 of iron ore; but not until a comparatively recent period were they 

 traced to their source in the mountains. During the construction of 

 the Union Pacific Railroad some of the engineers visited the mines 

 and spoke of their future value. In the summer of 1868 I had 4 an op- 

 portunity of examining this region in company with Dr. Latham and 

 Judge Whitehead, of Wyoming, and found the mines much richer and 

 more extensive than had previously been supposed. We commenced our 

 examinations in the valleys of the smaller branches of the "Chug" as 

 they emerge from the mountains, and found that the stray masses of 

 iron ore were confined to one of them. Following the branch up into 

 the rauge we soon came to the ore beds themselves, which we found to 

 be interstratified among the red feldspathic granites which compose 

 the nucleus of the range. The ore beds incline in the same direction 

 with the granites, and have the same joints and cleavage, and the ex- 

 amples of slicken-sides are numerous. They are not continuous, and 

 are confined to a restricted area, yet Mr. Whitehead traced one of the 

 beds a distance of over one and a half miles. The ore is located much 

 like that in the Lake Superior region, and is probably of the age of 

 the Laurentian rocks of Canada. The quantity of ore in this locality 

 appears to be unlimited. Thousands of tons have been washed down 

 into the valley of the "Chug" and distributed among the superficial 

 drift. As we leave the ore beds themselves these stray masses are 

 larger and more angular, and as we pass down the "Chug" they dwindle 

 to minute pebbles and disappear. Mr. J. P. Carson, of New York, an 

 assistant in the survey of 1868, made the following analysis of this 

 ore, at the school of mines, Columbia College : 



Sesquioxide of iron 45.03 



Protoxide 17.96 



Silica 0.76 



Titanic acid 23.19 



Alumina 3.98 



Sesquioxide of chromium 2.15 



Sesquioxide of manganese 1.53 



Lime 1.11 



Oxide of zinc 0.47 



Magnesia 1.56 



Sulphur 1.44 



Phosphorus a trace 



Fe . . , 45.49 99.78 



