Vanadiferous Minerals in Western Colorado. 129 



been securely closed by planking, and no examination of their 

 inner ends conld be made. I am thus unable to tell what 

 becomes of the deposit as it is followed in from the surface. 

 A few hundred pounds of picked carnotite ore has been 

 shipped from this claim and is reported to have sold for $1.25 

 a pound in Denver. The character of this deposit is similar 

 to others examined, except that in this case a well-defined fault 

 has provided a zone of crushed and porous rock in the hang- 

 ing wall, along which impregnation could take place. A few 

 hundred feet farther west the crushed sandstone adjoining the 

 fault has been impregnated with cupriferous solutions and is 

 spotted with stains of the blue and green carbonates of copper. 



Other Deposits. — It is known that several carnotite claims 

 have been taken up in Gypsum Valley in what is known as the 

 Disappointment District. The impregnated sandstone is said 

 to cap a hill and to constitute an extensive deposit, but it was 

 not visited. Carnotite is also reported from the Blue Mountain 

 District, but I have no personal knowledge of these occurrences. 

 It seems highly probable that the material will be found widely 

 distributed in the Mesozoic sandstones of western Colorado and 

 eastern Utah, although perhaps nowhere in very extensive 

 bodies. 



Origin of Deposits. — That the deposits of carnotite and ros- 

 coelite were formed subsequently to the deposition of the sand- 

 stones is evident from the facts presented in the preceding 

 pages. It is equally plain that the minerals could not have 

 resulted from the alteration, in place, of other compounds of 

 vanadium and uranium originally deposited with the sands. 

 The shape and position of the deposits indicate clearly that the 

 ores have been deposited in their present position only after 

 transportation from a greater or less distance. Moreover, the 

 recency of the deposits and the fact that they are sometimes 

 directly connected with faults and dislocations in the sand- 

 stones shows that the vanadium and uranium compounds could 

 not have been the original cementing material of the quartz 

 grains, but have in all probability locally replaced the calcite 

 which acts as matrix to the ordinary light- colored sandstone in 

 which the ore-bodies occur. The deposits of roscoelite appear 

 to be comparable to the impregnations of the sandstones with 

 cupriferous solutions observed in many places in this region, 

 particularly on La Sal Creek near Cashin and in Sinbad 

 'Valley, whereby the sandstone becomes colored bright green 

 with the carbonate of copper. In these cases, however, the 

 copper appears to have been previously deposited in part as 

 chalcocite. An analogy might also be drawn with the green 

 chromiferous sandstone near Placerville already referred to. 

 In all these cases the actual sources of the materials which have 



