474 \V. E. Hidden mid ./. B. Mackintosh — Yttria and, 



Art. LIX. — A drs<-ri/>tion of several Yttria and Thoria 

 Minerals from Llano Count//, Texas,' by W. E. Hidden 

 and J. B. Mackintosh. 



History. — In July, 1886, the first piece of gadolinite (a mass 

 of about 1^ lbs.) was accidentally discovered, by Mr. J. J. 

 Barringer, in Llano County, Texas. It was noticed projecting 

 from an outcropping of granite and was detached therefrom 

 and preserved merely because of its peculiar appearance. 

 Later Mr. Barringer commenced digging at the locality, and 

 in a short time he unearthed a pocket of huge crystals and 

 masses of this rare mineral aggregating not less than 500 kilos. 

 This remarkable quantity was obtained by digging with pick 

 and shovel, in the partly decomposed surface rock and all came 

 from a space not over 4 ft. deep, 3 ft. wide and 8 ft. long. 



Until August, 1888, the true nature of the mineral remained 

 unknown and meanwhile it received such local names as 

 "tin-ore," "black-jack zinc," " volcanic-glass," etc. Later the 

 name "samarskite" was given to it and as such it was known 

 until Mr. Barringer, upon sending it to New York in an 

 endeavor to find a market for it, received the information that 

 it was gadolinite. About this time it came under the notice of 

 one of us, and an effort was made to develop the locality thor- 

 oughly. Thus far only the gadolinite had been found and no 

 value having been attached to it the mineral, had been free to 

 all who desired u a few pounds of it." Of the large quantity 

 obtained in 1886, only about 100 kilos then remained; the 

 greater portion having been gradually distributed among local 

 visitors. In January of this year, realizing that a locality that 

 could produce the rare mineral gadolinite in such unprece- 

 dented masses as had already come under our notice, was 

 worthy of careful investigation, we sent Mr. Wm. Niven, of 

 New York, on a special visit to the region and it was the series 

 of specimens collected by him that induced one of us to person- 

 ally visit the locality. This was done during the past summer, 

 two months being spent in prospecting the whole region ; the 

 results of this investigation are embodied m this announcement. 



Description of locality. — The spot where the gadolinite has 

 been found is nearly five miles southward from Bluffton, in 

 Llano Co., Texas, and on the west bank of the Colorado River. 

 The whole surrounding region for many miles is Archaean* (with 

 occasional cappings of limestone), and granite, in various shades 

 of color and texture, is the common country rock. A coarse 

 textured deep-red granite is most abundant, and through it 



* See " Geologic story of the Colorado River." R. T. Hill, in American Geol- 

 ogist, vol. iii, No. 5, pp. 291-2. 



