I02 Bulletin of Laboratories of Denison University. [Voi. xi 



in the paper to the area immediately southwest of the Virgilina 

 district, in which occur both acid and basic eruptives, mostly- 

 acid, of pre-Cambrian age. 



Mr. W. H. Weed^ recently published a valuable paper 

 treating in some detail the type of ore deposits in this belt and 

 the important economic features. He refers to the rocks of 

 the district as follows : 



"The country-rock is schist, in a few places massive enough to be 

 called gneiss. . . . The rocks are all of igneous origin — even the 

 softest and most shaly show this character in thin sections under the 

 microscope. But in a few instances only is the igneous nature of the 

 schists recognizable to the eye. This was observed at the Thomas 

 mine, where a purplish rock is clearly a porphyritic meta-andesite. 

 These schists are cut by dikes of later igneous rock (diabase). The 

 only one seen by the writer was that exposed in the Blue Wing mine. 

 Apart from the dykes, however, I would say, on the 

 strength of field-observations alone, that the rocks are of igneous origin, 

 and belong to the various porphyries which have been discovered in 

 the Appalachian belt This conclusion is confirmed by the micro- 

 scopic examination of thin sections, which has shown the rocks to be 

 altered andesites, that is meta-andesites and andesite tuffs." 



General Field Characters and Occurrence. 



As seen from the accompanying map, the area is located 

 near the eastern border of the Piedmont plain, in Halifax 

 county, Virginia, and Person and Granville counties, in North 

 Carolina, 47 miles east of Danville. The belt occupies a low, 

 flat-topped, though somewhat conspicuous, ridge, which trends 

 a few degrees west of south and slopes very gradually to the 

 east and west. It will average 100 to 200 feet in elevation 

 above the neighboring stream valleys. The cross-drainages 

 are all small, but the ridge is flanked by several large ones on 

 the west and northwest sides. The ridge is traced northward 

 to the Dan River valley, in Virginia, some 10 miles north of 

 the state line. In North Carolina its southward extension is 

 estimated by Hanna" to be about 30 miles, reaching nearly to 

 Durham. Prospecting is confined, however, to an approxi- 



' Types of Copper Deposits in the Southern United States, Trans. Amer. 

 Inst. Min. Engrs., 1901, Vol. XXX, pp. 453, 454. 



' Ores of North Carolina, Raleigh, 1S88, p. 215. 



