fcpBNCER.] COPPER DEPOSITS AT PEARL, COLO. 165 
found on the dump the ore is seen to be chalcopyrite occurring 
with ferruginous zinc blende in a segregation vein composed mostly 
of hornblende, but carrying a small amount of calcite. The country 
rock is very platy or schistose, but the vein material seems to be 
massive. The relations of the sulphides to the hornblende and cal- 
cite show that they are contemporaneous minerals. Unfortunately 
the vein does not afford a visible outcrop, so that its relations to the 
country rock can not be studied in detail. 
Sierra Madre shaft. — This property is located near the State line 
and about 1-J miles north of Pearl. A mineralized zone about 7 feet 
in width, having a course N. G0° E., occurs in dark micaceous gneiss. 
This zone, which is parallel to the structure of the gneiss, may be 
divided into two portions, one of which is made up of entirely mas- 
sive hornblende, free from banding and carrying pyrite, chalcopyrite, 
and zinc blende, with a small amount of galena; the other portion is 
a light-colored banded rock resembling the sugary granite mentioned 
as occurring near the Big Creek shaft. This portion of the vein car- 
ries zinc blende and a small amount of pyrite, in bands parallel with 
the course of the mineralized zone. The hornblende vein presents no 
sharp walls against the inclosing gneiss or against the siliceous por- 
tion of the mineralized zone, and it seems to have been formed by seg- 
regation accompanying the general metamorphism wiiich produced 
the banding of the country rocks. 
The zinc blende occurring in the siliceous gneiss possibly replaces 
the dark-colored minerals which it originally contained, and was 
probabty introduced at the time the hornblende vein was formed. 
Lizzie and Tally claims. — These are contiguous properties tying less 
than half a mile north of Pearl. In this region there are rapid 
alternations of granite and diorite in many varieties. The mineral- 
ized zones seem to conform to the structure of the gneiss, which has a 
course about N. 50° E. The two shafts appear to be located upon 
different zones, and still other zones are present upon the claims. In 
both shafts bornite and chalcocite have been found, but these minerals 
are confined to the upper portions of the workings. 
Swede or Hawkey e group. — These claims lie about 2 miles south- 
east of the town. In general the occurrence of the ores seems to be 
similar to that in the Big Creek and Sierra Madre claims. Granite is 
the usual country rock, but bands of diorite are also present, and the 
immediate walls of the ore-bearing material are of an intermediate 
type of rock. At the Copper Crown shaft, which is the principal 
opening, the course of the vein is N. 10° W. The vein matter is con- 
siderably weathered, but consists of pyrite, chalcopyrite, and zinc 
blende, occurring in a gangue of calcite and serpentine. Occasional 
specimens show that the serpentine has been derived from the altera- 
tion of hornblende or pyroxene, which indicates that the deposit is of 
the same nature as the Sierra Madre. 
