580 E. T. Wherry — New Occurrence of Carnotite. 



association of these elements uranium and vanadium with coal, 

 pointed out more particularly by Clarke,* has a similar signifi- 

 cance. The upper portion of the Pottsville formation in the 

 Mauch Chunk region contains interbedded coal seams, the 

 development of which was certainly connected with the favor- 

 able stimulus to plant growth resulting from the same change 

 of climate which made possible the formation of the carnotite. 

 In general, even though the association is not a genetic one, it 

 seems reasonable to expect that, whenever the period preced- 

 ing that of coal formation has been so dry that dark silicates 

 have been broken up and transported to the points where the* 

 coal flora is to develop without extensive decomposition, the 

 elements uranium and vanadium may be looked for as con- 

 stituents of the ash. Or, in other words, in their presence or 

 absence, we may have a new method of throwing light on cer- 

 tain details of the climatic conditions of past geologic times. 



Summary. 



1. Carnotite has been discovered in a new locality, Mauch 

 Chunk, Carbon County, Pennsylvania. 



2. As it agrees in composition with material from Colorado 

 and South Australia, and these agree among themselves better 

 than has usually been supposed, carnotite is entitled to be 

 classed as a distinct mineral species, with the formula (Ca,K 2 ) 

 (U0 2 ) 2 (V0 4 \, belonging to the uranite group. 



3. The vanadium and probably the uranium also have been 

 extracted by circulating surface waters from black shales, 

 which have been formed in the midst of conglomerates by 

 mechanical concentration of dark minerals from the crystalline 

 rocks to the south and east, following the change from arid to 

 moist climatic conditions at the beginning of Pennsylvanian 

 time. 



4. As the Colorado deposits occur in a similar position, their 

 origin may have been the same, and it is suggested that the 

 frequent association of these elements with coal may also be 

 connected with such a climatic change. 



Lehigh University, South Bethlehem, Pa., 

 February 26, 1912. 



*Bull. IT. S. Geol. Survey No. 491, pp. 672-678, 1911. 



