216 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
in/' below into the San Juan breccia), which, in the vicinity of the 
mine, is decomposed and weathered near the surface. Snch cropping 
as may formerly have been visible have been covered by the shaft 
house and other mine buildings. The mine was formerly worked by 
a vertical shaft over 1,000 feet in depoh, which in 1809 was nearly full 
of water, rendering the workings wholly inaccessible. 
T. E. Schwarz 1 described the Yankee Girl ore in 1883 as occurring 
"in four chimneys, three near the south side of a dike and the fourth 
near the north side of another dike some distance away. The ore in 
each chimney is similar and often occurs in bowlder form." In 188(i 
Mr. S. F. Emmons made a brief visit to the mine and recorded his 
observations in the following notes, not hitherto published: 
The main shaft is sunk about on a level with the road, but the old tunnel runs 
in from the bottom of the valley below, which slopes here very steeply; the tunnel 
cuts the shaft about 75 feet from the surface. From the top of the shaft down 
to the tunnel level the ore was lead ore, mainly galena and pyrite. From the 
tunnel level down the ore began to change, copper coming in and lead disappear- 
ing; below the third level is practically no lead. The rich ore is now a purple cop- 
per ore with stromeyerite, copper glance, copper pyrite, and some gray copper and 
barite. Outside the ore body the country rock is impregnated with fine-grained 
pyrite. In the Orphan Boy, one of the Yankee Girl , claims, is some manganese 
spar, but it is not at all common. 
The mine has six levels, the adit making the first. The sixth level is at a depth 
of 500 feet. The shaft has been sunk 113 feet deeper, and a station made for a 
seventh level, which has not yet been opened. 
The ore is found in several cylindrical or elliptical chimneys, called, respectively, 
the Yankee Girl, Orphan Boy, North, West, and South chimneys. The main 
shaft was sunk about in the middle of one of these chimneys — the Yankee Girl. 
The discovery shaft, about 50 feet north of the main shaft, was 10 feet down in 
this body when the mine was finally purchased for $125,000. In the first and 
second levels the main shaft is still in this chimney, but below it is cut at an ever- 
increasing distance south. The chimney is nearly cylindrical in shape, 20 to :-:0 
feet in diameter, and consists of white quartz rock, more or less impregnated 
with mineral. Around this is country rock, somewhat decomposed, and impreg- 
nated with pyrite— a sort of transition material; beyond this is unaltered breccia. 
Dike rock, according to Schwarz, is always within 15 feet or less of the ore shoot. 
The west drift on each level, running off as a rule a little south of the shaft, 
generally cuts through the " dike rock " and finds another chimney beyond it. 
But the shape of the dike is very irregular; in one drift it is over 100 feet wide, in 
the next below almost wanting, and comes in again in the next below. Accord- 
ing to Schwarz it sometimes runs quite flat for a considerable distance. Herecog 
nizes two dikes running in his ground, and another running from the Guston 
into the Robinson. I observed many joint planes or cross fractures, some showing 
slickensided surfaces, and these generally form walls to the ore bodies. Although 
these have a prevailing direction northwest, there are many other directions, and 
their surfaces are sometimes curving. It is my impression that such planes have 
admitted or given form to the ore bodies, and Schwarz admits that there is always 
a prominent one running with the longer axis of the ore body, which often tapers 
up into it when running out. 
Kaolin occurs, presumably pure, but resembling Chinese talc, although not so 
translucent. Bournonite and enargite occur in the Yankee Girl; also polybasite 
in the upper part. 
Proc. Colo. Sci. Soc, Vol. I, 18s:$ M, p. UfcJ. 
