126 KEMP'S ORE DEPOSITS. 



2.03.08. Example I2cl Colorado Magnetites. Beds of mag- 

 netite of a lenticular character in rocks described as syenite (Chaf- 

 fee County) and diorite (Fremont County). With these a number of 

 others are mentioned which vary from the example, but of which 

 more information is needed before they can be well classified. The 

 last are mere prospects. The mines in Chaffee County have been the 

 only actual producers. There are three principal claims the Cal- 

 umet, Hecla, and Smithfield. They extend continuously over 4000 

 feet. The wall rock is called syenite. Chauvenet describes them 

 as having resulted from the oxidation of pyrites, and as being in 

 rocks of Silurian age. They average 57$ Fe, with only 0.009 P, 

 but are comparatively high in S, reaching 0.1 to 2.0& These mines 

 and those at the Hot Springs, mentioned under Example 2, have 

 furnished the Pueblo furnaces with most of their stock. The de- 

 posit in Fremont County is at Iron Mountain, but is too titanifer- 

 ous to be valuable. It is a lenticular mass in so-called diorite. A 

 large ore body has been reported from Costillo County, in limestone 

 (Census Report) or syenite (Rolker). In Gunnison County, at the 

 Iron King and Cumberland mines, excellent ore occurs in quartz- 

 ites and limestones, called Silurian. At Ashcroft, near Aspen, 

 high up on the northern side of the Elk Mountains, is a great bed 

 or vein of magnetite, in limestones of Carboniferous age, with 

 abundant eruptive rocks near. It is thought by Devereux to be al- 

 tered pyrite. Still, pyrite is a common thing with magnetite else- 

 where. There are other smaller deposits in Boulder County and 

 elsewhere in the State. 1 



2.03.09. In Wyoming an immense mass of titaniferous magne- 

 tite is known near Chugwater Creek. It is described by Hague as 

 resembling a great dike in granite. 2 Gabbro is in the neighborhood. 



2.03.10. Example I2e. California Magnetite. Beds of mag- 

 netite of lenticular shape in metamorphic slates and limestones on 

 the western slope of the Sierra Nevada. Others of different char- 

 acter are also known. In Sierra and Placer counties lenses of 

 excellent ore are found, accompanying an extended stratum of lime- 



1 R. Chauvenet, " Papers on Iron Prospects of Colorado," Ann. Heps. 

 Colo. State School of Mines, 1885 and 1887 ; also M. E., Denver meeting, 

 1889. Rec. W. B. Devereux, " Notes on Iron Prospects in Pitkin County, 

 Colorado," M. E., XII. 608. B. T. Putnam, Tenth Census, Vol. XV., p. 

 472. Rec. C. M. Rolker, " Notes on Iron Ore Deposits in Colorado," 

 M. E., XIV. 266. Rec. 



2 " Iron Mountain, Wyoming," 4Qth Parallel Survey, Vol. II., p. 14. 



