FICTILE MATERIALS. 655 



for safes and for similar purposes. Thorough search in the continuation of 

 the Burnetian axes (in a course north 75° west by south 75° east from the 

 outcrops referred to) may reveal other workable deposits. The appearance, 

 however, is that of local metamorphism, and the exposures thus far observed 

 are all in situations where more than the usual amount of plutonic action has 

 been developed. The acidic schists of Burnetian age and much of the quartz- 

 ite of the Texian System can be utilized as fire resistants, and in adaptable 

 situations the basic schists of all the pre-Cambrian periods can be so employed. 

 There is no lack of refractory materials, and none of them are difficult of ac- 

 cess. Asbestos was reported last year as probably absent from the district. 

 A little of this mineral was collected by Mr. G. Jermy, while engaged upon 

 the Survey, in Gillespie County. The amount is not great, but the quality is 

 good. Very much of what passes for asbestos is either fibrolite, aragorrite, or 

 chrysolite, all of which minerals occur in the region in crystalline forms not 

 very different from the fibrous asbestos in the eyes of untrained observers. 

 For further descriptions of the refractory products see pages 374, 375 of the 

 Report for 1889. 



IV. FICTILE MATERIALS. 



The pottery clays may be represented in some of the finer grades of argil- 

 laceous material deposited along the stream courses, but few have been tested 

 sufficiently to give any report upon their adaptations. In many parts of the 

 Burnetian areas and elsewhere the feldspathic granites and acidic porphyries 

 yield excellent material by their decay, but it is necessary to find the locali- 

 ties in which the most pure detritus has been quietly laid down by water. 

 Clear Creek, in Burnet County, and much of the region westward, in Llano 

 County; parts of the outskirts south of the King Mountains, and the district 

 south of Enchanted Rock, are among the best situations for such accumula- 

 tions. The district north of Llano, eastward, may also have some similar 

 tracts, but these will not be traceable across wide intervening areas. See also 

 remarks on pages 375, 376, of 1879 Report, under head of "Materials for 

 Glass and Pottery.'' 



Glass sands are abundant in restricted portions of the Cambrian exposures, 

 as especially over the country north and northeast of Valley Spring, and at 

 the head of Cold Creek west, where pure white sand, as " wash" and as lightly 

 consolidated beach deposits, obscures the surface and forms bluffs and castel- 

 lated buttes. Untested material of good appearance also occurs in the Trinity 

 Sands along the Cretaceous border. Other supplies might perhaps be ob- 

 tained, if required, from the disintegration of sandy schists of Burnetian age. 



