lOlJf^ Ceetain Mineral Resoueces 5 



turn was succeeded by a long period of erosion and weathering. 

 The rocks have suffered to a variable degree from all these 

 factors. In general, each formation has a massive and a mashed 

 or schistose phase, with every gradation between the two. The 

 passage of heated solutions has affected all formations, as evi- 

 denced by the mineralized zones, the abundance of quartz veins, 

 and the high degree of silicification in many belts of rocks, and 

 the universal occurrence of infiltrated iron ores. Finally, 

 erosion has planed off all the upper portion of the folded series ; 

 but weathering has proceeded in excess of erosion to such an 

 extent that the region is now deeply decayed, so that only here 

 and there do the rocks project through a thick mantle of decom- 

 posed rock or soil. 



In the Georgia belt ^ the rocks are of Archsean micaceous and 

 hornblendic gneisses and schists and probably represent the 

 sheared granitic and dioritic rocks. These gneisses and schists 

 are banded in narrow lenticular-shaped layers, from two to 

 twenty feet wide. A dark-colored schistose hornblende rock, 

 locally known as " brick-bat," is of frequent occurrence. Its 

 structural relations are very difficult to determine; at times it 

 is conformably interlaminated with the other schists (as at the 

 Hedwig mine, near Auraria) ; again, it appears to have no 

 reg-ular relation in its position to the adjoining schists, which 

 are cut off by it or very markedly disturbed in their strike, 

 bending around the " brick-bat " mass, and developing a crum- 

 pled or folded structure in the schistose laminae (as at the Single- 

 ton and Lockhart mines, nearDahlonego). It is possible that these 

 " brick-bat " masses, which appear to be dioritic in origin, are 

 mag-matic segregations or blebs, similar to the pyroxenic and 

 hornblendic blebs of the South Mountain region of l^orth Caro- 

 lina, though, as a rule, larger. The prevailing strike of the 

 gneisses and schists is north 20°-30° east, and the dip 

 30°-60° southeast. Locally, however, in the presence of the 

 dioritic masses, this changes to northwest strikes with northeast 

 dips. The rocks are often garnetiferous and contain rarer 

 accessory minerals, such as monazite, though to a much lesser 



2 Bull. 10, North Carolina Geological Survey, 1897, pp. 21-22. 



