IRON. 619 



wide exposures in some areas. The outcrops of the magnetite are less understood in this 

 belt, because the country is fenced in and not easy to investigate. It is also a tract which 

 has many complications, and one which had to be neglected in part last season (1889) for 

 lack of time to work it properly. Still the belt was crossed by us with section lines in four 

 places, and several special reconnoissances were made in other parts, so that a generally 

 correct idea has been obtained of the economic situation. The indications are good for the 

 discovery of important masses of iron ore in the district, but at present I am unable to 

 clearly define the position of the magnetite except by analogy with the outcrops of other 

 belts. Much of this tract is covered by thick deposits of the later sediments (Cambrian, 

 etc.), and granitic irruptions and other complications have made rather a puzzling structure. 

 But there are two or three parallel lines trending northwest across the area in which the 

 hematites are well developed, from which I judge that the magnetites are not very far to 

 seek in certain outcrops. 



Having had better opportunities to study this region in 1890, I am now- 

 prepared to define with some degree of certainty the positions of two distinct 

 bands which are indicated upon the accompanying Economic Map. Of these 

 the more eastern line of outcrop passes not far from Oxford Postoffice and a 

 short distance south and west of Field Creek. The actual exposures are 

 probably not as prominent as might be inferred from the map, but the course 

 of the band is correctly indicated thereon. Its relations to the parallel belt 

 farther west are somewhat close, and it may be that the intervening territory 

 may not be found to be barren in all parts; but the general relations of the 

 two bands are shown with moderate precision as they have been drawn upon 

 my map. The iron ores, however, have been cut out along a considerable 

 portion of the line, and this band therefore can not be considered as promis- 

 ing a field for iron mining along its whole course, as is the case with a num- 

 ber of others in the region. The complications of structure in western Llano 

 County are not easily defined in general terms, although they are not difficult 

 to understand when one has the key supplied by a knowledge of the different 

 geologic systems. The best manner of searching for the hard ores in this 

 band is to employ a dipping needle, and to obtain a fair acquaintance with 

 the Fernandian rocks in their typical exposures. Slips, faults, contortions, 

 and other results of numerous disturbances of the strata, besides the effect of 

 irregular erosion, have made it very difficult for any but a skilled engineer 

 with unstinted time at his disposal to successfully follow the courses of the 

 iron ores in this region. They often crop out well developed in unforeseen 

 situations, and again they disappear as suddenly where the complications of 

 structure seem least evident at the surface. The Barder tract, on surveys 330 

 and 331, Llano County, affords a good illustration of this confusion, although 

 it also yields some of the best ores of the Oxford band in great abundance. 

 Nos. 7 and 8, Table III, are average samples. 



The Oxford band is also exposed to some extent in the region around 

 Blowout, Blanco County. 



