Vanadiferous Minerals in Western Colorado. 121 



ent on preexistent vanadiferous sandstones. For the carnotite 

 of Montrose and Mesa Counties, as mentioned by the French 

 authors, occurs mixed in all proportions with quartz-sand 

 grains, the remnants beyond doubt of former sandstone bodies, 

 and it was soon recognized that in the carnotite bodies the 

 vanadium existed in two conditions, the larger part by far as 

 pentavalent vanadium in the easily soluble carnotite, and a 

 smaller and sometimes hardly distinguishable portion as triva- 

 lent vanadium in a much less soluble silicate which was free 

 from uranium. 



It was hoped that by a field reconnaissance, observations 

 bearing on these points would be obtained and material assem- 

 bled which would on analysis help to solve the nature and 

 explain the association of these two entirely different classes of 

 mineral substances. 



The field and microscopical observations of Messrs. Ransome 

 and Spencer are embodied in the pages immediately following 

 these introductory remarks. Unfortunately their collections, 

 except from Placerville, came to hand so late that the chemical 

 work on the more western occurrences has been confined to 

 the carnotite bodies alone, of which material was already in 

 my hands. Greenish sandstones have been observed by Messrs. 

 Ransome and Spencer in those regions, but whether any of 

 them are highly vanadiferous, or what their connection with 

 the carnotite may be, remains yet unknown. The only two 

 examined did not owe their color to vanadium. Meanwhile 

 the chemical results thus far obtained, which it is advisable to 

 put on record at once, will be found in the concluding section 

 of this paper. 



In this place it is my pleasure to record my appreciation of 

 the readiness with which the following gentlemen have sup- 

 plied me with material for study : Messrs. Poulot and Voilleque 

 of Denver, Mr. A. B. Frenzel of Placerville, and Mr. J. P. 

 Duling of Paradox. These gentlemen have, also, not hesi- 

 tated to furnish me with all information at their disposal as to 

 occurrence, etc., of these interesting ore bodies. 



Occurrence of the Uranium and Vanadium Ores. 



F. L. RANSOME. 



General. — In the autumn of 1899, a brief reconnaissance 

 trip was undertaken into the western portions of San Miguel, 

 Montrose and Mesa Counties, near the Utah-Colorado line. I 

 was accompanied by Dr. A. C. Spencer, whose knowledge 

 of the stratigraphy of the region was of great assistance. 

 The primary object of the expedition in accordance with a 

 suggestion from Mr. S. F. Emmons, was to investigate the 



