104 DESCEIPTIVE GEOLOGY. 



feet above the surrounding country, and commanding a grand view of the 

 Laramie Plains and the low country to the north, with a panoramic out- 

 line, 100 miles in length, of the Park Range to the west, while the peak 

 itself suggests the prominent, bold quartzite summits in the descriptions of 

 Scandinavian scenery in the Archaean regions of Northern Europe. The 

 main ridge has a trend approximately north 20° east, with what appears to 

 be the strike of the rocks. The dip is to the eastward at a high angle. No 

 accurate measurements of the thickness of the formation could be made, but 

 it certainly is not much under 2,000 feet, while escarpments cut 1,500 feet 

 deep through brilliant white rock. The quartzite is compact, brittle, with a 

 uniform texture. It is traversed by thin, irregular iron seams, and in places 

 is slightly stained a pale red from the oxidation of the iron. Crystals of 

 quartz and feldspar are exceedingly rare. 



Near the base of the formation, the quartzite has a pale bluish tinge, 

 is somewhat coarser-grained, with interstratified beds of smooth and rounded 

 quartz pebbles, many of them having been pressed and elongated in the 

 direction of the strata since their deposition, showing conclusively their sed- 

 imentary origin. They vary in size from that of a pea to a hen's egg. 



The rock from the summit yielded — 



Sihca 94.333 



Ignition .........: 0.269 



the residue showing considerable quantity of alumina, with traces of iron 

 and lime. A large part of the alumina present in the quartzite would appear 

 to be segregated, as nearly pure, simple silicate of alumina, in the form of 

 cyanite, which was observed at rare intervals in narrow veins or seams a 

 few inches in width. The cyanite occurs in long crystals of a pale-blue 

 color, with a pearly lustre and hardness not above 5. It is associated with 

 colorless quartz, but free from all accumulations of iron. 



Another marked feature of this formation is the number of nan-ow, 

 well-defined dikes of dark intrusive rock, which penetrate it at a number 

 of localities on the west side. The widest observed was 20 feet, with a 

 strike northwest and southeast, or against the observed strike of the beds. 

 They are probably diorites. The only one from which a specimen was 



