MANGANESE. 605 



carrying only from two to ten per cent of manganese in the Survey samples. 

 Table II gives analyses from these localities. 



Within the last few months the southeastward prolongation of the Spiller 

 Belt has been prospected, and some promising manganese deposits have been 

 brought to light. It is probable that many more outcrops or easily exposable 

 occurrences of similar material will be discovered by careful scrutiny over 

 intervening areas. At present the best known exposures are near the bound- 

 ary line between Blanco and Gillespie counties, along the drainage basin of 

 North Grape Creek. Excellent surface croppings, apparently of transported 

 material, have been found on the eastern half of survey No. 251 (William 

 Starrock league), Blanco County. In much of the area, however, the later 

 rocks now cover the natural position of the veins too deeply to give any hope 

 of profitable returns from working them, while another large portion of the 

 the tract has been denuded of the whole set of rocks in which the manganese 

 ores were originally entombed. Parallel belts cross the Rutersville College 

 survey, No. 217, Gillespie County, and these have been exposed at various 

 points along the vein courses as indicated upon the map. 



THE PACKSADDLE BELT. 



The region referred to in the Report for 1889 (page 346) lying " between 

 Packsaddle Mountain and the Riley Mountains," including " that portion of the 

 district in which the northwest strike is at the surface," has been examined 

 more thoroughly since then, and the conditions affecting the occurrence of 

 manganese and its distribution have been more clearly made out. The pro- 

 longation of the belt northwestward in Llano County, through the region of 

 Horse Mountain and its extension southeastward into Blanco County, are 

 well known. In both directions some prospecting work has been done. The 

 results do not materially change the conclusions drawn by the writer last 

 year. The products are not strictly speaking manganese ores, but more prop- 

 erly manganiferous iron ores. Some of them may have a decided commercial 

 value eventually in the manufacture of ferro-manganese, or in the production 

 of manganese steel. From a geologic standpoint — i. e., regarding their mode 

 of origin — they are allied to the true manganese ores more closely than to 

 the original iron ores. In other words, they are secondary products and 

 associated with the limonites. They have the same structural relations and 

 occur under the same conditions as the manganese and manganiferous ores 

 of the Spiller Belt. Peculiar features of both districts are the high silica 

 contents and the low percentages of water, etc. ("loss on ignition"), although 

 the association with the limestones is intimate, and calcite is not infrequent 

 as an accompanying product. This may, perhaps, be explained by reference 



