16 DESCRIPTIVE GEOLOGY. 



Samples of tlie coarse granular variety, collected from the deposits 

 south of Iron Mountain, yielded Mr. R W. "Woodward the following: 



Metallic iron 34.29 - 



Titanic acid 49.47 



All the samples examined gave a very high, although a varying, 

 amount of titanic acid. 



This high percentage of so refractory a substance as titanic acid renders 

 the vast deposits of iron of but little use for practical purposes in iron- 

 smelting, which is to be regretted, as the beds in the Laramie Hills could be 

 easily mined, and are so well located in reference to a market, and the 

 known sources of iron in Wyoming are so limited. 



The titanic-iron deposits of Canada and Norway would appear to pos- 

 sess very much of the same general characters, with equally varying amounts 

 of titanic acid in their composition. An analysis of a specimen from Kra- 

 geroe in Norway^ gave as high as 46.92 per cent, in titanic acid, and Dr. T. 

 Sterry Hunt^ found 48.60 per cent, from similarly-situated beds at Bay 

 Saint Paul, Canada. The ilmenite from Chateau Richer gave, titanic acid, 

 39.86 per cent. 



This occurrence of ilmenite and gabbro, so intimately associated to- 

 gether in Laurentian rocks in widely-separated parts of the globe, each 

 with the same physical habits, and, in the case of the gabbros of Wyoming 

 and Norway, with the same minute microscopical structure and peculiari- 

 ties, is most remarkable, and the causes evidently deep-seated. 



Another mineral, graphite, common to the Laurentian series, is found 

 on the west side of the hills in considerable quantities, in thin beds and 

 seams. Two varieties are known: one a compact, hard mineral, made up 

 of laminae of graphite scales, and finely-disseminated pyrites in thin plates, 

 which gives a bronze color to the mineral ; it is very friable, and the pyrites 

 on exposure undergoes a partial decomposition. A sample yielded 27 per 

 cent, of iron-pyrites, rendering the graphite too impure to be of any 

 economic value. The second variety crumbles easily to a fine granular 

 powder, is iron-gray in color, and occurs mixed with fine quartz sand, which 

 gives it somewhat the appearance of magnetic sand; the pure powder, 



^Daua's Miueralogy, 1868, 145. ^Qeological Survey of Canada, 1863, 501. 



