362 T . L. WATSON— VIRGILINA COPPER DISTRICT 



green in color and as fibrous and frayed-out masses. A more common 

 occurrence perhaps, is as a felt of actinolite needles admixed with the 

 other constituents, particularly chlorite, epidote, and iron oxide The 

 needles are very long and slender and are frequently much curved and 

 bent. The pleochroism of the actinolite is usually quite strong 

 No trace of either augite or olivine was indicated in any of the slides. 



sl'toTt lAF ea% alt6red C ° nditi0n ° f the r6ek8 ' it ™™ not be 

 safe to state that they were not present as original constituents 



Chlorite is a constant and abundant constituent of the rocks, but is 

 variable in amount, and presents the usual occurrence for such rocks. 

 A striking feature is the intimately associated grains arid plates of epi- 

 dote distributed through the chloritic mass in a manner to indicate the 

 simultaneous development of the two minerals, a characteristic occur- 

 rence in some of the Lake Superior greenstones described by Williams * 

 Clements t has shown that in some of the basic volcanics of the Hemlock 

 formation the great abundance of chlorite in some sections is more than 

 could result from the alteration of that amount of the original bisilicate 

 present and points out that it is derived in part from the altered glassy 

 base This explanation is likely applicable to some of the sections of 

 the Virgilma rocks, since the amount of chlorite is in excess of the orig- 

 inal bisihcate, and is probably a derived product in part from an altered 

 glassy base. 



Epidote in the form of small and large irregular grains and plates is 

 abundantly present, closely associated with the chlorite and amphibole. 

 It varies in color from deep yellow to nearly colorless grains, with high 

 single and double refraction, and showing strong pleochroism in the col- 

 ^"t* 4 The ^mewhat isomorphic plates show the M(001) 

 and 1 (100) cleavages in their usual development. 



Zoisite, when identified, was closely intergrown with the epidote 

 forming an epidote-zoisite aggregate, the individuals of which are dif- 

 ferentiated 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. 



* Bulletin no. 62, U. S. Geol. Survey, 1890, p. 56 et seq. 

 t Monograph no. xxxvi, V. ,8. Geol. Surrey, 1899, p. 101. 



