PETROGRAPHY— QUAETZITES. 475 



of mica scattered through it, and is similar to [38]. It is a characteristic 

 crystalline quartzite. 



That from Warren Peaks [210] is similar in color and luster to the 

 above, though a little more reddish. In the section, the quartz is observed 

 to be sharp and crystalline, with a few crystals of transparent mica through 

 it and occasionally some brown mica, 



In [211], from the mouth of French Creek, the quartz is again crys- 

 talline and clear, containing very large cavities and good sized microlites, 

 strongly dichroitic, changing from yellowish-green to red with the analyzer 

 alone. They may be hornblende, as there are some larger crystals having 

 the same peculiarity. The brown mica present is much less dichroitic. 

 The color of the rock is light-gray. 



The rock from Amphibious Creek [212] is made up of rounded grains 

 of quartz, which are full of particles of a black mineral, probably mag- 

 netite, and exceedingly minute microlites. The section is so opaque from 

 the presence of large quantities of oxide of iron that it is difficult to render 

 it sufficiently transparent for observation. 



In [215], from French Creek, the quartz is very pure and crystalline, 

 with numerous cavities and microlites. There are also transparent mica 

 and some opaque masses, probably a darker and weathered mica. 



The rock from Rapid Creek [202] is a glauconitic limestone. Under 

 the microscope, the mass of rock consists of a whitish crystalline mineral, 

 which polarizes feebly, changing only from light to dark, while the lines of 

 cleavage are very distinct. This mineral has in every way the appearance 

 of calcite. Sparingly scattered through the limestone are pellucid and 

 brilliantly polarizing grains of quartz. There are also some brown masses 

 and occasionally a rounded, green body of finely granular texture. These 

 are the glauconite grains, the brown ones being the same almost entirely 

 decomposed. In some cases merely a thin, brown crust remains lining the 

 inside of the cavity. The hand specimen was not at hand to examine and 

 compare with the observations in the section. 



The glauconitic sandstone [203] from Rapid Creek shows under the 

 microscope that it consists of quartz and glauconite in about equal propor- 

 tions, held together by a dark-brown cement. The quartz grains are mostly 



