RECONNAISSANCE EXAMINATION OF THE COPPER DEPOSITS 
AT PEARL, COLO. 
By Arthur C. Spencer. 
DESCRIPTION OF THE REGION. 
Pearl, Colo., lias been a post-office for several years, but only within 
the last three years has it become known as a mining camp. It is 
located in Larimer County, near the northern boundary of Colorado, 
about 20 miles southeast of Encampment, Wyo., and an equal dis- 
tance south of the New Rambler copper mine. 
The area contiguous to Pearl over which active prospecting has been 
carried on for the last three years is drained by a tributary of the 
North Platte River, now known as Big Creek, but represented on the 
maps of the Fortieth Parallel Survey as Grange Creek. The region 
is mountainous, lying as it does in the heart of the Sierra Madre, or 
northern end of the Park Range, which forms the westernmost of the 
three elevated zones which compose the Rocky Mountains in this lati- 
tude. The crest of the Sierra Madre, from 10 to 25 miles south and 
west of Pearl, forms the continental divide separating the waters of 
Big Creek from the head of Elk River, which flows to the Yampa 
and thus to the Green River. 
Eastward from Pearl there is an easy line of travel to North Park, 
and toward the west the old Government road leading from Laramie 
to Hahns Peak gives a route to the head of Encampment River. 
The town itself is picturesquely situated in a broad basin near the 
junction of several wide valleys, which give access to all parts of the 
adjacent mountains. The elevation of this basin is about 8,000 feet, 
but within a distance of 10 miles there are mountains which rise to an 
altitude of from 10,000 to 12,000 feet. 
The surrounding slopes are covered by a dense growth of pine and 
spruce, while the valley bottoms, which were originally covered by a 
luxuriant growth of wild grass, are now devoted to the cultivation of 
timothy and other grasses for hay. 
GENERAL GEOLOGY. 
The geology of the region is similar to that of a portion of the 
Encampment district, though the pre-Cambrian quartzite, which is 
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