THE LESSER METALS. 



263 



and pyrolusite, often in concretionary masses, disseminated through 

 residual clay, which with the ores has formed by the alteration of 

 limestones and shales. The deposits are entirely analogous to 

 Examples 2 and 2, under " Iron." Along the Appalachians 

 the favorite horizon is just over the Cambrian (Potsdam) quartzite. 

 Such is the case at Brandon and South Wallingford, Vt., where 

 the ores occur in a great bed of clay between quartzite and lime- 

 stone. They are referred to under Example 2a, where mention is 

 made of the associated limonites and interesting lignite. They 

 have never been important producers of manganese. Crimora, in 



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SECTION NO. 2. 



SECTION NO. 4. 



FIG. 63. Sections of the Crimora manganese mine, Virginia. The trough 



is formed by Potsdam sandstone and is filled with clay carrying 



nodules of ore. After C. E. Hall, M. E., June, 1891. 



Augusta County, Virginia, is the largest mine in the country. The 

 containing clay bed is very thick, as a drill hole of 276 feet failed 

 to strike rock. The ores occur in pockets, which as a maximum 

 are 5 to 6 feet thick and 20 to 30 feet long, and of lenticular 

 shape. Other irregular stringers and smaller masses run through 

 the clay, which preserves the structure of the original rock. 

 Potsdam quartzite underlies it. Other similar bodies occur at 

 Lyndhurst and elsewhere in the Great Valley of Virginia. Less 

 important deposits are found at higher horizons. Cartersville, 

 Ga., is second to Crimora in production. The ores again occur in 

 pockets in a stiff clay and are associated with quartzite, which is 

 not sharply identified as yet. It may be Cambrian (Potsdam) or 

 Tipper Silurian (Medina). West of Cartersville is the Cave Spring 



