iron. 627 



of magnetite, and the iron segregations in the Cambrian sandstones at High 

 Point may be connected with such a buried deposit. The southeastward pro- 

 longation of this line passes near other concretionary accumulations, but my 

 observations tend to the conclusion that these and many other isolated or 

 irregularly disposed patches are rather the remnants or partial exposures of 

 an extensive Cambrian bed which covered much of the region formerly. 

 This is rendered more probable from the leanness of the ore and its altered 

 character. The outcrops of the blue marbles may serve, however, as indi- 

 cators of the positions of buried iron ores which it may be possible to reach 

 by prospect shafts. 



THE MARBLE FALLS BAND. 



A vein course of much importance carrying in parts of its outcrop some 

 excellent ore is approximately plotted as passing a little east of Marble Falls; 

 thence northwestward through the Logan Vandivier survey, No. 206, Burnet 

 County; thence in the same course, crossing the Shinbone near where that 

 ridge is intersected by the Austin and Northwestern Railway; and so on 

 through Backbone Ridge and across the northern end of Long Mountain 

 (Llano County). There are indications of the same band at different points 

 in -both directions beyond the limits here named, and wherever the ore has 

 been tested in the outcrops it has been found rather abundant and of good 

 quality. Analyses Nos. 43 and 44 are fair samples of the ordinary yield. 



THE CHEROKEE-TIGER MILL BAND. 



The vein course which approximately extends the Babyhead magnetite 

 band through the border areas of sedimentary rocks is not as well denned as 

 some others, partly because it is cut out by denudation in many places, even 

 to the exclusion of the Fernandian supplying rocks, and partly from the lack 

 of opportunity for the exposure — perhaps also for the formation — of veins 

 upon the large scale.* There is a suspicion, which has not yet been fully 

 confirmed, that the limonitic veins do not penetrate the San Saba Series, at 

 least in the upper (Deep Creek) division. f As much of the area northwest- 

 ward in San Saba County is covered by the San Saba Series, the lack of vein 

 exposures in this patn may possibly thus be explained. But, as the decom- 



*I should be glad to speak authoritatively concerning one feature of structure which is 

 still unsolved in the Silurian area. The plans of my Division of the Survey for 1891 con- 

 template the settlement of the question, if it be possible, by wider observations. The prob- 

 lem is to determine the true relations of the San Saba and the Leon scries, and the distribu- 

 tion of the veins may afford the clue which is now lacking. 



\ This would seem to imply that the Deep Creek division, and perhaps also the Hinton 

 division, should really be included in the Niagarian (Upper Silurian) System. 



