360 T. L, WATSON — VIRGILINA COPPER DISTRICT 



istic of the purple-colored rocks. The rocks vary in color from some 

 shade of medium to dark green (the prevailing color) to a slate purple. 



The rocks are aphanitic in texture, displaying at times a distinct por- 

 phyritic structure in the massive phases, which becomes more apparent 

 under the microscope. The massive phases of the rock are indicated at 

 several places within a few miles to the north and south of the town of 

 Virgilina. With one exception, this type is prevailingly dark in color, 

 showing on close examination a mingling of green and purplish shades, 

 with the greenish tint so predominant that the rock appears dark green 

 on first glance. Both the characteristic chlorite and epidote shades of 

 green are contrasted at times in the same specimen. On a freshly broken 

 surface the fracture is conchoidal to subconchoidal, with a more or less 

 waxy luster. 



Approximately half a mile south of Virgilina a shallow opening 

 (Cornfield) is made, showing the massive rock in its least altered con- 

 dition (analysis I). The rock is porphyritic in structure and the color 

 is a medium dark-purplish shade, which contrasts with the surrounding 

 more altered green schistose rock. 



Epidote of the usual pistachio-green color enters largely in places into 

 the composition of the rocks, and it is mixed locally in considerable 

 proportion with white quartz as a vein mineral. The schistose green- 

 stone is easily scratched with the knife, and suggests approximately the 

 same degree of hardness as that of ordinary clay slate. 



At the Copper World mine, 61 miles south of Virgilina, in the Caro- 

 lina portion of the belt, a partially loose-textured, fine-grained, purple 

 rock is mixed with the surrounding green schists. The material bears 

 every resemblance to a tuff* and is streaked in places' by the character- 

 istic actinolite shade of green due to alteration, and contains inclosures 

 of a dark-colored massive material, usually of small but varying dimen- 

 sions and partially rounded in outline. The fragmental or clastic nature 

 of the mass is plainly visible. The microscope confirms the clastic 

 nature of this rock and shows that it is composed of fragments of igne- 

 ous rocks of the same character and composition as the igneous rocks of 

 the district. Microscopic study also indicates the presence of similar 

 clastic material at a number of other points in the district. 



No trace of the amygdaloidal structure, so characteristic of the South 

 Mountain and Lake Superior basic greenstone areas, has been observed 

 in the Virgilina rock. 



MICROSCOPY OF THE ROCKS 



The rocks vary in texture from dense aphanitic to medium fine-grained, 

 with the porphyritic structure shown usually in the massive types. The 



*See Weed, W. H., op. cit. 



