MANGANESE ORES. 345 



4. TIN. 



The same might be said of tin as of zinc, were it not for claims which have 

 been made of the discovery of the former in two or three separate localities. 

 On this account, and because of the receipt of a very fine crystal of cassiterite 

 (tin oxide) from a gentleman who did not seem to know its nature, and who 

 stated that it came from the stream " wash " near the point where he gave it 

 to me, I have taken much pains to search for tin ore. Failing to get react- 

 ions for this metal in any of the minerals of my own or my assistants' collec- 

 tions, Mr. Huppertz was specially charged with the examination of the locality 

 referred to above and of the adjoining region, in the hope that more of the 

 same material might be found. But the quest has been fruitless. The area 

 is an extension of the Barringer tract, and one not unlikely to yield tin min- 

 erals, if they exist at all in the Central Mineral Region. 



Great care has also been exercised to detect tin in the rare minerals of the 

 immediate Barringer district. To this date (May 1, 1890) no evidences of 

 the presence of the metal in any combination have been seen by me anywhere, 

 although I have examined critically more than 8000 specimens collected from 

 various parts of my district. There are areas in Blanco and Gillespie coun- 

 ties which I have not worked over except in the most cursory manner. Of 

 these it is impossible to speak authoritatively at present, but such collections 

 of the Survey as have come under my inspection certainly contain no tin. 



III. MANGANESE ORES. 



Although manganese occurs in many places as a constituent of limonitic 

 iron ores in veins, and occasionally as jet black, glossy streaks of braunite or 

 manganite in crevices in special situations, there are only one or two restricted 

 districts which are liable to become producers of manganese ore upon a com- 

 mercial scale. The Spiller mine, in the mountains, or rather in the foot-hills, 

 south of Fly Gap, has an extended local reputation because of the money 

 expended by its owners in boring with the diamond drill, ostensibly to test 

 the continuity of the deposit in depth. This is really the only known occur- 

 rence of such ore upon an extensive scale anywhere in this region; but as 

 there is nothing in its environment to indicate strictly local conditions of 

 accumulation, it is hardly likely that diligent search will be unrewarded by 

 the discovery of similar deposits. In fact, the writer has already traced out 

 several probable companion belts in the neighborhood of the Spiller mine by 

 surface croppings as good as are commonly used as indications in other States. 

 The quartz, which is well exposed west of Schussler's and north of Brown's, 

 about one mile or less northeast of the Spiller mine, is much stained with 

 manganese oxide. The course made out here is north 25 degrees east for the 



