IRON. 617 



extension of the band across the areas southeast of the Riley Mountains, as 

 far as the scarp of later rocks which obscures it near Blowout, in Blanco 

 County. 



The Cold Creek Area. — By reference to the Economic Map, it will be seen 

 that the upper valley of Cold Creek is traversed in part by the northwestern 

 outcrop of the Iron Mountain band. Some very choice ore has been taken 

 from this district in Simpson's pasture and at other points in the course of 

 the band between Sponge Mountain, in Llano County, and the Cambrian es- 

 carpment near the Fredonia and Cherokee road, in San Saba County. In all 

 respects the features are very minutely identical with those in the other tracts 

 to be described in this same band. Development has not gone far enough to 

 determine the quantities available, but the only doubt upon that point arises 

 from the apparently greater plutonic or igneous action in this district, al- 

 though that may really be more favorable than otherwise. In this particular 

 there are certain resemblances to the conditions surrounding the Lake Su- 

 perior ores. The time may come when the State of Texas shall be able to 

 appropriate funds sufficient to enable all these details to be studied carefully. 

 A vast amount of material has been collected bearing upon questions con- 

 nected with the origin and history of the ores, but the Survey has not yet the 

 facilities for elucidating the subject. 



The "Iron Mountain'" Outcrop. — About one mile and a half northwest from Valley Spring 

 Postoffice, upon the right bank of Johnson Creek, the ground slopes somewhat steeply beyond 

 the old flood plain of the stream, and at the culmination of the hill a small ridge or mound 

 formerly stood out in relief. This was the condition at the date of the writer's first visit, in 

 June, 1889, but by the time it was again examined, in the following August, the excavations 

 made in the so-called Iron Mountain had changed its appearance, so that now it would be 

 difficult to understand this nomenclature. The course of the iron ore and its probable per- 

 sistency in the northwest trend was clearly made out when I first examined the locality, 

 and the excavation of numerous pits all over the adjoining space was unnecessary, as has 

 been proved by the results, which fully confirm my original views regarding the strike and 

 character of the mass. The section of the rocks at this point is given under the head of 

 Fernandian System, in Part I of this Report. The quantity of magnetite and hematite at 

 this outcrop is very great, and the explorations made have increased the knowledge of its 

 extent.* 



The occurrence of a very high phosphorus hematite layer upon one side of 

 this outcrop is peculiar, as almost no phosphorus exists in the average of the 

 ore. A reference to the section given under the head of the Iron Mountain 

 Series in the last Reportf will explain the probable cause of this streak. A 

 band of altered binary granite is there associated with the magnetite, and in 

 this is a green phosphatic mineral. The adjoining thin layer of the iron ore 

 is thus contaminated with phosphorus. As in some samples from this streak 



* First Annual Report, p. 351. 

 fPage 271. 



