REPORT OF THE DIRECTOR I9II I57 



Graphite is abundant in scales and plates arranged parallel to the 

 distinct foliation. Very commonly the graphite is somewhat split or 

 even shredded, with chlorite, sericite and pyrite filling its inter- 

 spaces into which they have evidently penetrated after the 

 crystallization of the graphite. Like the graphite, pyrite is usually 

 elongated parallel to the foliation, occurring most often in irregular 

 grains. The section shows one of the veinlets seen in the hand 

 specimen. It is made up of many fine anastamosing branches parallel 

 to the foliation, the pyrite often showing distinct crystal form, while 

 the outer margins of the vein are bordered with the sericite, whose 

 position and arrangement are so evidently controlled by the vein 

 that there can be no doubt that the sericite formed after the pyrite 

 (see figure 21). That the latter mineral is a replacement of the 

 ordinary constituents of the rock seems equally certain, being 

 localized by solutions circulating in relatively porous parts of the 

 rock. Had the replacement proceeded further an ore similar to those 

 actually worked would have resulted. 



The foot wall of the Stella ore body is a much coarser rock than 

 the preceding, lighter colored and less prominently foliated. Large 

 cleavage faces of feldspar are shown and many scattered grains of 

 pyrite, but the pyrite veinlets so conspicuous in the hanging wall 

 are lacking. In thin section, orthoclase is very abundant, passing 

 over into the usual greenish, nearly isotropic, chloritic alteration 

 product. j\Iica is thoroughly bleached, or completely .altered to 

 chlorite. There are some large areas of clear interlocking quartz 

 possibly of vein origin. As a whole the section suggests a much 

 altered, sheared pegmatite or injection gneiss. No graphite is shown 

 and pyrite is not abundant, occurring as rather evenly disseminated, 

 irregular grains which have a tendency to lie in chlorite, though 

 there are abundant exceptions to this rule. The pyrite often shows a 

 variety of skeletal growth, having the interspaces filled with chlorite 

 and sericite, as shown in figure 22. Here there is a green, low 

 refracting, chloritic alteration of feldspar clearly shown in process 

 of formation, in the large feldspar grain on the right, and the same 

 material filling cavities in the pyrite, near the bottom. Apparently 

 this is older than the pyrite. Quite distinct from this is the filling 

 of the spaces between the slender tongues of pyrite, by nearly color- 

 I less, strongly doubly refracting sericite, clearly younger than the 

 pyrite. Pyrite is also seen replacing orthoclase and bleached mica. 

 It is, perhaps, worthy of note that the disseminated pyrite is quite 

 as abundant in this rock lacking graphite as in the hanging rock 

 containing the latter in abundance. 



