Thoria Minerals from Llano County, Texas. 477 



Most of the gadolinite is altered into a brownish-red mineral 

 of waxy luster; some of the masses are entirely so altered, 

 while in others the change has only taken place superficially. 

 A further alteration has been to a yellowish-brown, earthy 

 (ochreous) substance which upon drying in the open air becomes 

 a very light powder. The average size of the masses of this 

 Texas gadolinite has been in our experience about half a pound ; 

 though embedded crystals (hydrated) were noticed not above 

 . half an inch long by one-quarter inch wide (very acutely termi- 

 nated) and as to large masses there were many of 5, 10 and 15 

 lbs. each. One double crystal weighed forty-two lbs. and was 

 nearly free from matrix. Another huge pointed mass, in real- 

 ity a crystal, weighed fully sixty pounds. * All of the gado- 

 linite had at some time in the past presented smooth crystal 

 surfaces (as the hydrated crust often gave evidences of), but 

 very few masses were found without more or less exterior altera- 

 tion. This alteration had roughened the underlying surface 

 and had given a dark brick-red color to all the changed mineral. 



On only three crystals were we enabled to find sufficiently 

 smooth surfaces to give us even approximate angles, and these 

 we here append : 



1^1= 115°-m£° Ai-i- 145°-146' 



I~ 1 = 156°-158|° l-i^i-i (ov. 0) = 111°-112° 



1^1= 119°-119£° ~ I = 90°-9r 



1 „ = 113°-113f 1 ^ 1 (ov. i-i) = 77°-79° 



— 1 * +1 (ov. 0) = 46° $-i~ 1 = 123°-126° 



All the crystals observed were lengthened in the direction 

 of the vertical axis (in one instance ten inches long), and the 

 plus and minus 1 and 2 pyramids are present often to the total 

 extinction of the basal pinacoid, making acute forms difficult 

 to extract from the matrix in perfect condition. A distinctly 

 monoclinic habit was apparent in many of the masses, and the 

 pyramid 2 was often developed only upon the plus or minus 

 side. The basal plane was only noticed in one instance. At 

 another vein, one mile south, two crystals of gadolinite, of rare 

 beauty and perfection, were found on the land of Mr. Hiram 

 Casner ; this goes to show that other discoveries of the rare 

 minerals are possible in the neighborhood. 



Yttrialtte, a new Thorium- Yttrium silicate. 



The mineral which we have named Yttrialite was dis- 

 covered associated with, and often upon, the gadolinite, and 

 but for its characteristic orange-yellow surface alteration (that 

 of gadolinite immediately along side of it being invariably of 

 a dull brick-red color) it might have continued to pass for 

 " green-gadolinite," which was the local name given to it. Of 

 these yellowish masses one weighed over ten pounds, and 



* Stated on the authority of Mr. Barringer and many of his neighbors. 



