372 T. L. WATSON VIRGILINA COPPER DISTRICT 



Van Hise and Clements regard the greenstone schists of the Crystal 

 Falls iron-bearing district as altered diabase, diabase-porphyry, and 

 gabbro.* Clements f has shown the derivation of the greenstones of 

 the Hemlock formation to be from original basaltic and andesitic rocks. 



The evidence here adduced from the descriptions of the rocks of the 

 several areas indicates the striking fact that the present altered rock 5 

 greenstone, is remarkably similar for the several districts, but when, 

 through chemical and microscopic means, they are traced to the original 

 rock, distinct differentiation, such as distinguishes the various basic 

 igneous types from each other, is shown. Moreover, not only is this 

 striking similarity indicated in the altered rock in each instance, but the 

 processes involved in producing the alteration have been uniformly 

 alike. The alteration has been one of structural and chemical metamor- 

 phism, resulting in the formation of abundant chlorite and epidote and 

 smaller amounts of other secondary minerals and the accompanying 

 secondarv schistose structure. 



The deposits of the immediate district are copper, with those of work- 

 able iron ore reported from other portions of the same counties. Copper 

 prospecting in the district dates back forty or fifty years. The Gillis cop- 

 per mine was opened in 1856, § exposing a large body of copper glance. 

 Systematic work is of recent date, however. 



The ore occurs mostly in quartzose veins, and to a limited extent as 

 finely divided particles disseminated through the rocks in places. The 

 workable ore is confined entirely to the veins. The vein stone consists 

 principally of quartz with considerable calcite and epidote mixed locally. 

 The altered country rock, greenstone, is intimately mixed with the 

 quartz and calcite as thin lenses and stringers, which impart/in places, a 

 banded structure to the vein. The included portions of the altered rock 

 vary from mere films and dark streaks in the quartz to a preponderance 

 of the schist with quartz infiltrated between the layers. The quartz is 

 further frequently encased by layers of the schist wrapped around it. 



The workable ore comprises glance and bornite mixed with the green 

 carbonate, malachite — an alteration product from the original sulphides. 

 A considerable sprinkling of the red oxide and native copper are seen in 



*Mono. U. S. G-eol. Survey, vol. xxxvi, pp. 484-486 ; ibid., vol. xxviii, pp. 203-208. 



flbid., vol. xxxvi, pp. 95-148. 



X For a detailed description of the individual mines and the general features of the belt as a 

 whole, see AV. H. Weed, Trans. Amer. Inst. Min. Engrs., 1901, vol. xxx, pp. 449-504. An earlier 

 account is given by Geo. B. Hanna in Ores of North Carolina, 1888, pp. 214-220. 



gEmmons, E., Geol. Survey of North Carolina, 1856, p. 344. 



