bansome.] DEPOSITS OF RED MOUNTAIN REGION. 217 
Iii a paper published in 1888 Mr. Emmons 1 says: 
In the Yankee Girl there are several chimneys in which the ore occurs. They 
are of elliptical outline, the longer axis corresponding in direction with a main 
system of fractures running through the region. Although the striated surfaces 
of these planes show that there has been movement along them, there is but little 
evidence left of actual brecciation of the country rock, the ore solutions having 
completely replaced the andesitic country rock between the fracture planes which 
gave access to them; in places a siliceous skeleton is left, the basic constituents 
being replaced by vein material; in other places a solid body of metallic minerals 
is found, while the country rock adjoining the body of pay ore is impregnated to 
a considerable distance with low-grade sulphnrets. 
This same year (1888) Mr. Emmons paid a second visit to the 
Yankee Girl. He found 2 thai on the sixth level, t32 feei deep accord- 
ing to Schwai'/, the Yankee Girl ore body was connected by ore with 
fche< >rplian Boy, a small ore "chimney," Lying in the upper levels about 
150 feet south oi the Yankee Girl. On this level the Yankee Girl ore 
body was elliptical in plan, L0 feet wide, and 32 feet long. At the 
fifth level it was nearly cylindrical, 8 to L0 feel in diameter, and 
nearly solid galena, passing below into "gray copperore." Just below 
the sixth level occurred a "floor" or horizontal fault plane. This 
varied from 3 inches to a fool or more in thickness, of clayey 
attrition material, ami frequently contained rounded masses of ore 
with rock centers. It dipped to the westward, sometimes as much as 
25°. There seemed to him to have been some movement along this 
floor to the westward or downhill toward the valley, but thai the ore 
bodies had not been much displaced. A third or "west ore body" 
lay to the westward of the Yankee Girl shoot, lenticular in shape, 
with ils longer diameter nearly north and south. On the sixth level 
this was 2 or 3 feet wide and 8 or 10 feet long, but with rather 
poorly defined boundaries, the ore fading off into mineralized country 
rock. 
Mr. Emmons records that — 
Around each chimney of ore is an envelope of *• quartz. - " This is a blue siliceous 
material, sometimes granular looking, sometimes compact and almost jaspery, 
and yet in the mass full of cracks, and sometimes of vesicles which are filled 
with white kaolin. It is generally impregnated with fine-grained pyrite. The 
ore, moreover, fills little fine cracks or seams down to an eighth of an inch in 
width. These are sometimes large enough to he worth taking out in the vicinity 
of the ore body. Outside the " quartz " envelope comes the "white rock, v which 
is evidently altered porphyry, which passes into a hard, compact blue rock, which 
is probably the less altered variety. 
What was called quartz at that time in the mine, Mr. Emmons con- 
siders at the present time to have been a jasperoid or siliceous replace- 
ment of the country rock. He also states that replacement is very 
abundant in the volcanic breccia, the matrix being first replaced by 
ore, which finally coats the pebbles or fragments of the breccia. 
1 structural relations of ore deposits: Trans. Am. Inst. Min. Eng., Vol. XVI, 1888, p. 834. 
2 Unpublished notes. 
