USEFUL METALS 251 



weighing 500 Ib. have been obtained. These nodules are scat- 

 tered through a ydlowitb-bfOWD Hay that form a nearly \ < ; 

 layer between a decomposed granite and the residual material 

 derived from a quartzose mica schist. 



'The more important deposits of the Appalachian Valley area 

 occur in a series of irregularly distributed materials along the 

 west foot of the Blue Ridge mountains for a distance of about 150 

 miles. The manganese ores occur in pockets in the clays of 

 residual or sedimentary character along the contact of the Lower 

 Cambrian quartzites with the overlying formations. 



There are many scattered occurrences of manganese ores along 

 the Appalachian belt in the more northern portion of the area. 

 Those in the western part of Vermont at Brandon, are the most 

 important and these have from time to time been mined. The 

 ore is psilomelane. Both pyrolusite and braunite are found in 

 Brandon, Bennington and Plymouth. Rhodonite occurs in 

 Topsham, Vermont, near the village of Waits River in masses 

 of sufficient size to be of considerable commercial value for decora- 

 tive interior work, but the value of the material was largely 

 destroyed through prospecting for chalcopyrite in the 60's. 



(2) Central District. The most important manganese deposits 

 of the central belt are found in the neighborhood of Batesville, 

 Arkansas. The ores are derived from the decomposition of the 

 Ordovician, Silurian, and Carboniferous limestones. The lower 

 deposits, perhaps enriched by the leaching of the Silurian ores, 

 are the most important because of their higher manganese content 

 and their greater freedom from phosphorus. 



(3) Cordilleran Section. Alabandite occurs on Snake River, 

 Colorado, along with rhodochrosite, argentite, and galenite. 

 The manganese silver minerals occur at Leadville, Colorado. 

 In Utah the oxides of manganese occur in the residual deposits 

 from the Triassic limestones. 



(4) Pacific Coast Belt. Two localities in California contain 

 manganese deposits. The first of these consists of pyrolusite 

 and psilomelane which occur in veins in Calaveras formations 

 of Carboniferous age in Plumas County and elsewhere in the 

 Sierra Nevada Mountains. The second field lies along the 

 coast, both to the north and to the south of San Francisco. The 

 ores appear as thin lenses, interbedded with the jaspers of the 

 Franciscan formations of Jura-Trias age. At the Ladd mine 

 the ore bodies are found as cavity fillings, infiltrations, replace- 



