IRON. 621 



ous iron ores in origin, and it is especially characteristic of areas in which 

 several axes of uplift cross. The occurrences are of much scientific interest, 

 and they afford important evidence concerning the geologic history of the 

 region. No deposits of this kind have yet been found of sufficient richness 

 to pay for working. Although the ore itself is excellent, it is rather sparsely 

 scattered through the white quartz in veins of no great width, usually. A 

 similar situation for this material is in the quartz masses which lie in the 

 trend of the Burnetian rocks, as at Barringer Hill and elsewhere, but the 

 best deposits are of more recent date. Near Fleming's (Fly Gap Postoffice), in 

 Mason County, the quartz is largely of the north-south Texian trend, but the 

 garnets and other members of the Burnetian System are exposed in a decided 

 outcrop crossing the tract. There is another similar area of some importance 

 in the granitic region about the headwaters of Spring Creek, Burnet County, 

 in the neighborhood of Capitol Rock. Good outcrops occur on the J. M. 

 Sparks survey and on the D. L. Cross survey, and in other localities in that 

 vicinity. (See further under the head of Eastern Burnet County Band.) 



The hematites which fall to be treated elsewhere are without exception al- 

 terations of pre-existing ore bodies, and their distribution, irregular as it may 

 seem, is very closely dependent upon the situation of the underlying and 

 often inaccessible magnetite bands heretofore described. 



Table III sufficiently indicates the variety in composition and the general 

 distribution of the hematites of the belt region. The affinities to the mag- 

 netites are there shown by the gradations in the percentages of ferrous oxide. 

 Analyses Nos. 10, 11, 12, 13 are of ores from the Baby head band; Nos. 14 

 and 15 come from the Packsaddle manganese band, or near it; Nos. 16, 17, 

 18, 19, represent the Iron Mountain band; No. 20 came from the Oxford 

 band; Nos. 21 and 22 are Pontotoc band samples; No. 23 was taken in the 

 easternmost manganese band; Nos. 24 and 25 show fairly the character of 

 the westernmost band. 



2. COMMINUTED SANDY ORES. 



The interior region of the hard belt ores is bordered largely by outcrops 

 of the sedimentary beds of Cambrian time, dipping at low angles. The study 

 of the section of these later beds is rendered difficult by the very irregular 

 lithologic character of the basal strata which are in contact with the earlier 

 rocks. But this irregularity really facilitates the discovery of suitable posi- 

 tions in which to work the iron ore deposits, and it also affords valuable clues 

 to the nature of local outcrops. 



Where these basal Cambrian strata rest directly upon the Burnetian rocks 

 or upon Texian rocks (as a rule), or where they directly overlie barren por- 

 tions of the Fernandian System, they are apt to be lighter in color, less heavy, 



