and their Contact Zones. 



77 



reef then being as much as 15 inches, and it yielded about one 

 ounce per ton. It underlies in this adit west at from 70° to 

 80°. The gold occurs in a vertical shoot of some 20 feet 

 along the course of the reef. At the north end of the shoot 

 the reef narrows very much, and in one place is quite want- 

 ing, there being then nothing remaining but the two walls 

 almost in contact. To the southward of the shoot, so far as 

 the workings extend, the reef does not wedge out, but 

 becomes poor. 



The following sketch will illustrate the position of the 

 reef on the lower workings and in the centre of the shoot.* 



Diagram No. 5.— Sketch of the Quartz Vein at the Rob Roy 



Mine. 



a. Horse of silicious felsitic rock, containing much 

 ordinary and arsenical pyrites. 



b. Finely crystalline foliated contact rock, with a little 

 pyrites. In places it is very micaceous. 



c. White translucent vein quartz, about 8 inches in width, 

 with arsenical pyrites (yields about 1 ounce per ton). 



* Mr. Forsyth, the owner of this mine, who has had great practical ex- 

 perience in the Swift's Creek reefs, said to me in speaking of them — " The 

 reefs here, as a rule, always wedge out not far from the surface, and when 

 they wedge out the walls are very hard." The bearing of these statements 

 will, I think, be seen further on. 



