CRYSTALLINE CARNOTITE FROM UTAH 



By Frank L. Hess 



Of the United States Bureau of Mines 



and 



William F. Foshag 



Assistant Curator, United States National Museum 



OCCURRENCE 

 Contriliuted dy Frank L. Hess. 



The carnotite deposits of Colorado, Utah, and Arizona have been 

 watched carefully since they first became known, in the hope of 

 finding the mineral in visible crystals. Many specimens of a crystal- 

 line yellow uranium mineral have been collected, but when tested 

 they invariably proved to be the calcium mineral, tyuyamunite, so 

 that crystal form or waxy body was and may yet be taken as almost 

 surely indicating the mineral with the name of Siberian ancestry. 

 The carnotite fields have yielded a number of new minerals, vanoxite, 

 pintadoite, uvanite, rauvite, and rossite, and when in examining a 

 carnotite deposit on a little flat known as Bridger Jack, on the west 

 side of Cane Springs Pass which leads over a low shoulder of the 

 La Sal Mountains 16 miles southeast of Moab, I discovered veinlets 

 of a golden yellow mineral beautifully ciystallized in plates, the 

 broadest of which were between one and two millimeters across, I 

 did not know whether the mineral was a new one or an old one in a 

 new guise. 



The mineral formed compact crusts one or two millimeters thick 

 and 15 or 20 centimeters broad on the walls of narrow cracks. Where 

 the crusts did not entirely fill the cracks the exposed surface had a 

 dull greenish color and showed indistinct crystal terminations. 



The veinlets were in a buff porous sandstone of the McElmo forma- 

 tion, presumably of either Lower Cretaceous or Uj)per Jurassic age. 

 The rocks are here in the drainage basin of Grand River (now by 

 congressional enactm.ent the upper part of the Colorado) and erosion 

 has entirely removed the rocks above the McElmo. 



No. 2708.— Proceedings U. S. National Museum, Vol. 72, Art. 12 



58239—27 1 



