REPORT OF THE DIRECTOR I9II I5I 



of pyrite, it has not been of such a nature as to effect a comminution 

 of the rock constituents. 



THE STYLES MINE 



On the Styles farm, a few miles farther northeast, another small 

 prospect has been opened. Here again the pyrite is in the rusty 

 gneiss and its Grenville association is strikingly shown by the fact 

 that this gneiss is hardly more than twenty feet thick and has lime- 

 stone both above and below, as shown in figure ii. 



In addition to these rocks con 

 siderable pegmatite, carrying a 

 peculiar light brown tourmalin, 

 is present, a great deal lying on 



the dump. While much of the Fig. 1 1 Rusty gneiss and ore heavily shaded 



pegmatite is free from pyrite, other specimens show considerable 

 quantities of the mineral. Indeed some of the pegmatite is a 

 rather lean ore of pyrite, while the rich ore seems again 

 to be merely a part of the rusty gneiss carrying an unusually 

 large percentage of pyrite. As at the Cole mine, graphite is 

 conspicuous in the richer ore which also contains large amounts of 

 grayish green, soft chloritic material not conspicuous at the Cole 

 mine, but very abundant and characteristic at other localities. 

 Indeed, in many cases, it appears that the enrichment of ore is 

 roughly proportional to the development of this chloritic product. 



Thin sections of the Styles pegmatite show moderately developed 

 cataclastic structure, w^hich is of particular interest since it evidently 

 precedes the deposition of pyrite. The latter, with some chlorite 

 and sericite, spreads in a network through the cracks between the 

 mineral fragments recementing the fractured rock. But the process, 

 instead of stopping at this point, evidently continued as an actual 

 replacement of the mineral grains by pyrite, thus increasing the 

 latter at the expense of the former (see figures 12 and 13). This 

 may continue to the production of a rich ore. Indeed, among the 

 specimens collected the richest is quite probably a highly altered 

 pegmatite converted into an ore by this process of replacement. As 

 at the other localities, graphite is quite generally present. 



A section of another specimen of pegmatite shows the same 

 kataclastic structure, with pyrite filling cracks and from them spread- 

 ing into and replacing the original minerals. There is also a more 

 perfect development of crystal form of pyrite when in contact with 

 chlorite rather than with primary minerals. This relation as already 

 indicated is shown by sections from several localities and strongly 



