REPORT 



ON THE 



GEOLOGY AND MINERAL RESOURCES 



OF THE 



CENTRAL MINERAL REGION OF TEXAS, 



LYING CHIEFLY SOUTH OF THE SAN SABA RIVER AND NORTH OF THE PEDERNALES 

 RIVER, WEST OF BURNET AND EAST OF MENARDVILLE AND JUNCTION CITY. 



BY . THEO. B. COMSTOCK, F. O. S. A. 



SKELETON. 



PART L— GENERAL REVIEW OF GEOLOGIC STRUCTURE. 



Outline of the geologic groups, for use of persons engaged in prospecting and develop- 

 ment Statement of the classification adopted, with chart showing the various terranes in 

 chronologic order. General statement of the economic products of each main geologic 

 horizon. 



PART IL— ECONOMIC GEOLOGY. 



How to use the Report for practical purposes. Plan of this part. 



METALLIFEROUS DEPOSITS. 



Precious Metals. Gold. — Possible sources stated, with results of assays, etc. 

 Silver. — Sources of supply. Districts limited and ores discussed. 



Base Metals. Copper. — Belts defined, with descriptions of localities and cuts showing 

 structure. Lead. — Districts outlined; outcrops illustrated and described. Review of the 

 situation. Guide to prospectors. Table of assays for gold, silver, copper, and lead. Tin. — 

 Full discussion of the present situation, with cuts showing the geologic conditions where 

 tin ore has been found ; character of ore and mode of occurrence Uncertainty of discover- 

 ing the mineral in commercially important quantities. Zinc. — Absence from this district. 

 Unsupported claims of discovery of zinc blend in 1890. Manganese. — Areas in which ores 

 outcrop. Belts defined. Discussion of ores and modes of occurrence. Table II of analyses. 

 Iron. — Extent and importance of the ores of the district. Hints regarding the development 

 of the iron fields. Separation of the ores into five classes, individually discussed in detail, 

 with location, description, and full treatment of the six great belts, or axes, including im- 

 portant hints concerning the miniug of the ores. Table III, analyses of iron ores. Metal- 

 lurgic review of iron fields. Probable future of the iron industry. 



Building Stones. Granites. — Seven classes, distribution and economic value. Marbles. — 

 Three classes, their distribution and uses. Limestones and Dolomites. — Localities and char- 

 acter of material. Sandstones, Slates, Schists, Clays, and materials for Cements, Lime, Mor- 

 tars, etc. 



Refractory Materials. Fictile Materials. Materials for Paints. 



PART III— SUPPLEMENT. 



Additional notes on stratigraphic geology. 



[555] 



