26 Bulletin of Laboratories of Denison University. [Voi. xii 



described as an alteration product of gummite, occurring "in 

 small bright lemon-yellow fibrous masses, sometimes in imme- 

 diate contact with the gummite found coating the uraninite or, 

 per se, embedded in the albite immediately surrounding the 

 tourmaline and often invading the latter." In both Quebec 

 and North Carolina the mineral is an alteration product of gum- 

 mite, and, in this particular, its occurrence is similar for the 

 two localities, while in Georgia the occurrence is entirely differ- 

 ent, as will be noted in the following description. 



At Stone Mountain, Georgia, sixteen miles east of Atlanta, 

 the mineral uranophane is found as a distinct incrustation, coat- 

 ing the faces of many of the joint planes, which cut the gran- 

 ite boss. It varies from a sulphur yellow to lemon yellow in 

 color, the former predominating, and forms an irregular coat- 

 ing not exceeding one-eighth to one-sixteenth of an inch in 

 thickness, usually less. It is tipped or coated with the clear, 

 colorless, and transparent, drop-like forms of the mineral 

 hyalite. The two minerals are so intimately associated that it 

 is almost impossible to effect a complete separation of them. 



The Stone Mountain granite, with which the uranophane 

 is associated, is a light gray, medium-grained, biotite-bearing 

 muscovite granite, composed of quartz, orthoclase, microcline 

 and soda-lime (oligoclase) feldspar, muscovite and biotite, with 

 sporadic microscopic accessories. Fresh specimens of the 

 granite were analyzed by Packard in the Survey laboratory with 

 the following results: 



SiO., 



A1,0, 



FeO .... 



CaO 



MgO . . . . 



NajO 



K.,0 . ... 



H.fy (ignition) 



Total . . . 100.4 



Several tests were made b}' the writer on separate portions 

 of the granite for the presence of uranium, with negative re- 

 sults. The yellow powder gave the usual tests before the blow- 

 pipe for uranophane, Packard carefully separated, by means of 



