Art. VII.] Watson, Virgilina Copper District. 105 



ties. Faulted and slickensided surfaces are in evidence at 

 some of the mine openings. 



The rocks are further cut by numerous irregular quartz 

 veins, which contain the workable copper ores. The veins are 

 traced for a mile or more in length on the surface, and in most 

 cases they are more or less parallel, partially overlapping at the 

 ends, and trending north 5 to 10 degrees east. They are 

 grouped by Weed^ as true fissure veins, lenticular in shape, 

 though connecting, crossing at times the schistosity of the 

 rocks and at others parallel to it. The surface over most of the 

 district is much littered with white quartz fragments derived 

 from the disintegration of the veins. 



Petrography. 

 Macroscopic Descriptions. 



A pronounced schistose structure prevails, and only in a 

 few places do the rocks appear like massive eruptives in the 

 field. The degree of schistosity varies from the thin banding 

 of a gneiss to the typical foliation of micaceous schists. The 

 very finely banded structure is more characteristic 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 porphyritic structure in the massive phases, which be- 

 comes 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 con- 

 choidal to subconchoidal, with a more or less waxy luster. 



Approximately half a mile south of Virgilina a shallow 



* Trans. Amer. Inst. Min. Engrs., 1901, vol. xxx, p. 452. 



