Some time was spent during the month of August, 1901, in a field examination of the Virgilina copper district, and the specimens of the rocks and ores collected were subsequently studied in the laboratory. Study was principally confined, both in the field and laboratory, to the rocks of the area, to determine their nature and origin. The ores were given only secondary consideration.
The rocks have been designated slates by the earlier workers, which, according to present usage, would imply a metamorphosed sediment. In many instances the characteristic field appearance of the rocks is that of slate or schist, but in their altered phases they are shown, by structural, chemical, and petrographic evidence, to be igneous in origin. Their subsequent alteration developed a schistose structure and an abundance of chlorite, epidote, and a limited quantity of hornblende. These impart to the rock its uniform green color and give the . . .