440 J. M. BOUTWELL 
Character.—That part of this formation which outcrops in this 
region is made up of gray quartzite, with comparatively insignificant 
exceptions of cherty patches and intercalated limestone. This, the 
upper portion, is characterized by its general massiveness, both in 
bedding, which is rarely less than 4 and frequently 8 to 15 feet in 
thickness, and in absence of parting planes. On fresh fracture it is 
light brownish-gray in color, and it weathers to a glistening polished 
surface of a lighter whitish shade. The normal quartzite is fine, even- 
grained, and dense. The exceedingly brittle nature of the rock causes 
it to chip into sharply angular irregular fragments, or, when ground up 
in a fracture zone, to appear as a glistening white, sugary portion, 
inclosing less finely comminuted quartzite. The cleanness of the 
rock has been demonstrated by repeated chemical analyses, which 
show a very high percentage of silica. Thus analysis of a specimen 
of this quartzite from Big Cottonwood Canyon shows 95.80 per cent. 
of silica. 
These lithologic characteristics are maintained with remarkable 
uniformity throughout the formation. Exceptions noted within this 
district are so rare as to be insignificant. 
Topographically this quartzite stands up as knobs or ledgy 
massive blocks and as prominent broad spurs falling off by precipitous 
slopes. 
That part of this great formation which is not present in this area, 
embracing the middle and basal portions, outcrops in prominent cliffs 
just south of this district. Excepting a few thin limestone beds near its 
top, the middle portion is massive quartzite, and in the lower part the 
intercalated limestone members increase in number and thickness. 
In Big Cottonwood Canyon the massive, dense character of the quartz- 
ite is preserved, and a few limestones are iatercalated. A thin, crinoi- 
dal sandstone occurs about 130 feet from the top; a thin, pitted, 
cavernous, grayish-white quartzite, 460 feet below that; and a thinly 
banded, calcareous quartzite, 430 feet farther down. In Weber 
Canyon this great formation is most characteristically exposed as a 
massive, dense, homogencous quartzite. The insignificant exceptions 
are a curiously pitted and marked horizon of quartzite just below the 
top and a few thin limestones in the basal portion. 
Distribution and thickness—The main area of this formation 
