Mr. William Phillips on the Oxyd of Uranium, 113 



partly through granite, partly through schist.* A further search 

 enabled me to obtain several beautiful specimens containing many 

 varieties in the form of the crystal as well as in colour. The 

 crystals are for the most part well-defined, but the largest scarcely 

 exceed half a line in length or breadth, and some of them are 

 accompanied by black pecherz (Uran oxydule Haiiy) ; they were 

 found on, or in the cavities of, considerable blocks of a hard 

 substance enclosing portions of decomposed felspar ; but quartz 

 formed the principal part of the mass, which had decidedly the 

 character of being an aggregation resulting from the decomposition 

 of granite. The specimens in my possession, are for the most part 

 thinly coated with a black substance which I consider to be the 

 pecherz in a pulverulent form ; internally they are of a redish hue, 

 arising probably from iron, with which the mine abounds, and 

 occasionally some minute rounded portions of iron haematites may 

 be observed. The depth at which these blocks were found, 

 according to the best information I could obtain, was about 90 

 fathoms from the surface, in a copper vein. 



I also obtained many specimens containing beautiful and well 

 defined crystals of the oxyd of uranium from Tol Carn mine, 

 which is about two miles north of Carharack, and near St. Die. 

 The veins of Tol Carn mine pass through a decomposed granite, 

 of which the prevailing substance seems to be felspar, enclosing 

 portions of quartz and silvery mica. With this substance the vein 

 seems to have been filled in that part in which the oxyd of 

 uranium was found, but it was of a dark colour, and had attained, 

 though considerably friable, a texture much more firm than that 

 of the neighbouring country ; and as, on almost every specimen, 

 the crystals of the oxyd of uranium were accompanied by pecherz^ 



_ * Geol. Trans. Vol. 2. p. 152. 



Vol. hi. p 



