Art. VII.] Watson, Virgilina Copper District. 109 



plates is abundantly present, closely associated with chlorite 

 and ambiphole. It varies in color from deep yellow to nearly 

 colorless grains, with high single and double refraction, and 

 showing strong pleochroism in the colored individuals. The 

 somewhat idiomorphic plates show the M(ooi) and T(ioo) 

 cleavages in their usual development. 



Zoisite, when identified, was closely intergrown with the 

 epidote, forming an epidote-zoisite aggregate, the individuals of 

 which are differentiated by their contrasted double refraction. 



Iron oxide is extremely abundant in portions of some of 

 the sections, and to some degree in all. It is not all magnetite, 

 as indicated by the red color of much of it. It is separated 

 from the other constituents of the powdered rock by means of 

 the magnet. It occurs as minute grains and crystals, and is in 

 part primary and in part secondary. It is so abundant in some 

 sections as to entirely mask some of the other more important 

 constituents. Its secondary nature is frequently shown in its 

 peripheral position surrounding the iron-bearing constituent 

 from which it was derived. 



The remaining minerals occurring in the rocks present no 

 noteworthy features. 



In the thin-sections of the purple-colored slaty rocks of the 

 Copper World, Durgy, and Yancey mines and the "Slate 

 Vein," in the Carolina portion of the belt, and probably the 

 fissile greenstone from the Halifax Copper mine, in Virginia, 

 there is strong evidence for regarding the rocks as clastic vol- 

 canics. The evidence is less plain in some sections than in 

 others, on account of the extreme alteration having destroyed 

 nearly all trace of the rock structure. When the texture is not 

 entirely destroyed the microscope shows a clastic composed of 

 igneous fragments similar in all respects to the true igneous 

 rocks of the district.^ 



1 Through the kindness of Professor J. Morgan Clements, of the University 

 of Wisconsin, I have been able to examine and compare the slides of the simi- 

 lar volcanic rocks of the Lake Superior region, and the similarity, as remarked 

 by Professor Clements, is strikingly close to the rocks of the Virgilina district. 



Professor Clements very kindly examined the thin-sections of the Virginia- 



