120 Hillebrand and Ransome — Carnotite and Associated 



Art. XIV. — On Carnotite and Associated Vanadiferotis 

 Minerals in Western Colorado ; by W". F. Hillebrand and 

 F. Leslie Ransome. 



Introduction. 



W. F. HILLEBRAND. 



The rather wide-spread occurrence in western Colorado of 

 considerable quantities of a canary-yellow ore of uranium has 

 been known for a few years past. It has been marketed to 

 the extent of a few tons, but its mineralogical nature was 

 unknown or incorrectly surmised until about a year ago. 



In the spring of 1899 a specimen of this ore first reached 

 my hands through Dr. Geo. P. Merrill of the U. S. National 

 Museum, and was speedily recognized to contain a mineral or 

 minerals new to science. Within a week appeared the announce- 

 ment by MM. C. Friedel and E. Cumenge* of a new mineral, 

 carnotite, a hydrous vanadate of uranium and potassium, 

 obtained through Mr. Poulot of Denver, from Roc Creek, 

 Montrose Co., Colo. Mr. Poulot had already identified vana- 

 dium in it. It was at once seen, despite certain differences in 

 composition, that the two were identical. 



According to the French authors the mineral is of simple 

 composition, as above expressed, with only a little iron and 

 mere traces of Al, Ba, Cu, Pb, and also according to M. and 

 Mine. Curie, of the radio-active substances radium and polo- 

 nium. The empirical formula 2U 2 3 , V 2 B , K 2 0, 3H 2 0, was 

 assigned to it, some doubt attaching to the water. 



Since then I have been able to examine carnotite from sev- 

 eral localities in western Colorado, finding in each case the 

 same lack of agreement with the analyses of Friedel and 

 Cumenge. 



While engaged in this work there were brought to my atten- 

 tion certain more or less greenish sandstones from the vicinity 

 of Placerville on the San Miguel River, San Miguel Co., Colo., 

 which were said to be highly vanadiferous and of considerable 

 extent, and in which a zone a few inches thick was rather 

 strongly impregnated with a yellow mineral resembling and 

 probably identical with carnotite. This latter appeared also 

 scattered through the sandstone at other points in sporadic 

 small patches, sometimes only visible by aid of a lens. 



This occurrence led to the thought that the carnotite bodies 

 farther west might also be associated with existing or depend- 



*Bull. Soc. Chim. de Paris (3), xxi, 328, 1899; Bull. Soc. Franc. Min., xxii, 26, 

 1899; Comptes Rend., cxxviii, 532, 1899; Chemical News, lxxx, 16, 1899. The 

 papers as published in French differ slightly. 



