140 DESCRIPTIVE GEOLOGY. 



gives a decidedly reddish tint to the rock, while the latter is only observed 

 in brilliant acicular crystals. 



The following analysis was made by Mr. R. W. Woodward : 



Silica 78.49 



Alumina 11.63 



Ferrous oxide 1.76 



Soda . , : . - - 3.21 



Potassa '. 5.3 1 



Ignition — 0.45 



100.85 

 Specific gravity, 2.6. 



This analysis is characterized by a somewhat high percentage of silica. 

 At the bend of Little Snake River, below Camel Peak, the same red gneiss 

 is exposed, interbedded with the hornblende- rocks. 



On Buck Mountain, at the head of Elk River, on the west side of the 

 range, occurs a compact dark-gray crypto-crystalline hornblende-rock, 

 almost identical in lithological characters with the one described from the 

 head of Jack's Creek ; there is something in the physical habit of the 

 groundmass which suggests that they may both be interbedded intrusive 

 rocks. 



The essential minerals which form the large rock-masses of the Archaean 

 series of the Park Range are, so far as observed, like the minerals of the 

 other great ranges to the eastward, limited in numbers. The list comprises 

 quartz, ortlioclase, plagioclase, biotite, muscovite, hornblende, and epidote; 

 as accessory minerals, garnet, magnetite, and gold. Under the microscope 

 are detected, not already observed macroscopicall5^, chlorite and apatite. 



Epidote, as an essential constituent of the rock, was seen only at Bruin 

 Peak in deep-red granite, where it occurs in considerable quantities. It is 

 found, however, in one or two localities scattered through the coarser gran- 

 ites. Red garnets occur in the finer-grained mica-gneisses, usually very 

 small, but on Davis Peak they were found of considerable size. Fine 

 gold occurs in the stream-beds in the region of Buck Mountain, where 

 miners have been engaged in washing for this metal for several years i^ast. 



