220 
ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
At present the Yankee Girl shaft is about 1,050 feet in depth. A 
plan of the extensive levels shows an intricate maze of workings in 
which no linear system is discernible. The mass of the workings lie 
just west of the shaft, and in plan may be roughly inclosed in an irreg- 
ular triangle. A smaller extent of workings lies just east of the shaft. 
Inspection of the dump, as well as inquiry, shows that there was 
never much vein quartz associated with the ore. The "quartz" of 
the miners is very largely the bleachecl and silicified country rock 
adjacent to the nearly solid bodies of ore. Where vein quartz occurs 
it usually carries iron pyrite. Barite, in small masses and crystals, 
occurs embedded in the bornite. The chalcocite is generally inti- 
mately associated with small amounts of chalcopyrite. Some speci- 
mens show that the ore has been fractured and recemented by veinlets 
of calcite. The ore minerals observed on the dump were galena, 
sphalerite, chalcocite (stromeyerite), bornite, chalcopyrite, and pyrite. 
Cosalite was recognized in 1884, therefore, in the upper part of the 
deposit, and was analyzed by A. H. Low, 1 as follows. 
Anal //sis of cosalite from Yankee Girl mine. 
Constituent. 
Per cent. 
Constituent. 
Per cent. 
36.22 
8.70 
28. 22 
15.74 
Iron 
Sulphur (by difference) 
4.4* 
18 64 
Lead 
Co])per 

inn. on 
Prousfite and polybasite also occurred occasionally in the Yankee 
Girl ore bodies. 
All accounts of the Yankee Girl mine unite in emphasizing the 
chemical activity of the underground waters encountered in the work- 
ings. According to Schwarz 2 they contained "24 grains per gallon of 
sulphuric acid (S0 3 )." Candlesticks, picks, or other iron or steel tools 
left in this water become quickly coated with copper. Iron pipes and 
rails were rapidly destroyed, and the constant replacement of the 
piping and pumps necessary to handle the abundant water was a 
large item in the working expenses. All agree in stating that the 
water entered far less abundantly below the sixth level. Some who 
worked in the mine express it as being "not so bad " below that level. 
But closer inquiry usually elicits the information that it was less abun- 
dant but as much or even more corrosive than at the upper levels. 
The product of the Yankee Girl is roughly estimated at about 
$3,000,000. 
Robinson mine. — This mine is really a part of the Yankee Girl, 
both being worked together. It has produced some good ore, but 
1 Proc. Colo. Sci. Soc, Vol. I, 1884, p. 111. 
2 Trans. Am. Inst. Min. Eng., Vol. XVIII, 1889-90, p. 139, 
