48 ALASKA GEOLOGY 



of the slates in this region appeared to be quite constant, 

 indicating only a moderate degree of shattering of beds 

 that are essentially in place. 



It will be seen that neither for this place nor for Silver 

 Bay are we able to accept the ingenious theory of a pyro- 

 clastic diorite advanced by Dr. Geo. F. Becker. 1 



At the hot springs on Baranof Island near Sitka the 

 country rock is a highly metamorphic sandstone, often 

 schistose, and even gneissoid in appearance. It is inti- 

 mately penetrated by dikes and massive intrusions of 

 granite, which has caused, at least in part, the greater 

 metamorphism. These dikes often run along the strike 

 of the sandstone, causing much contortion of the beds, 

 and many fragments of schistose sandstone are included 

 in the granite. 



Mr. Devereux and Mr. Palache visited the Chicago 

 mine, on Baranof Island, one and one-half miles from the 

 head of Silver Bay, and at 1,400 feet elevation. The ap- 

 proach was over the same grits, greywackes, sandstones, 

 and thin shaly bands. The mine is a development tunnel 

 only. The quartz body is said to be continuous for three 

 or four miles, and consists of a banded bluish quartz or 

 chalcedony with lenses of pale pink rhodonite. The 

 outcrop is black with manganese stains. The walls 

 are slate and greenstone. The mineral content of the 

 quartz seems small, chiefly scales of pyrite and pyrrhotite. 

 Mispickel is found in the slate near by. Quartz veins, 

 bunches and stringers occur quite abundantly in the 

 slate. 



Mr. Gilbert climbed to the summit of Mount Verstovia, 

 2,800 feet high, directly back of Sitka, and found the same 

 conglomerate and sandstone all the way to the top. 



1 Gold Fields of Alaska, iSth Ann. Rep. U. S. Geol. Survey, pt. in, p. 43. 



1898. 



