ransome.] PRODUCTS OF SUPERFICIAL DECOMPOSITION. 87 
quartz and pale-green fluorite. It is also found in a quartz lode in Dry 
Gulch, but in smaller crystals. In the Tom Moore lode it was noted 
as minute brown prisms in quartz. On Sultan Mountain it has been 
obtained from the North Star mine, and occurs in moderate abund- 
ance in the Empire-Victoria lode. The mineral from the last-named 
locality is nearly black and probably contains considerable iron, thus 
approaching wolframite in composit ion. It is embedded in quartz and 
pale-green fluorite. 
This mineral, if found in sufficient qnantites, would be valuable as 
an ore of tungsten. It is doubtful, however, whether any of the 
above-mentioned deposits contain it in sufficient abundance to render 
possible its commercial extraction. 
PRODUCTS OF SUPERFICIAL DECOMPOSITION. 
Owing to the vigorous erosion to which the Silverton region has been 
subjected, oxidized ores have seldom had opportunity to accumulate 
to any great depth, and play a small part in mining operations. Small 
amounts of the carbonates of copper, malachite, and azurite, and the 
carbonate of lead, cerussite, can be found in the croppingsof most of 
the Lodes, and cerussite was mined to some extent from the upper 
levels of the Silver Lake mine. Anglesite, or sulphate of lead, also 
occurred near the surface in the Silver Lake and Whale lodes and 
formed an importan! pari of the ore body of the Zuni mine, where it 
resulted from the oxidation of guitermanite. Anglesite, resulting 
from the oxidation of galena and often containing kernels of the sul- 
phide, occurs in the Anaconda mine about three-fourths of a mile 
south of Cinnamon Pass, whence four or live carloads, carrying 55 per 
cent of lead and 11 to L8 ounces of silver per ton, have been shipped. 
In the Saratoga mine the greater part of the ore has been mined com- 
paratively near the surface, ami consisted of a soft mass of ferruginous 
clay carrying carbonate of lead and silver, probably native or as 
chloride. 
Under some circumstances partial oxidation has extended to depths 
of several hundred feet. In the Silver Lake mine more or less oxidation 
has taken place where the lodes of Group II join the Silver Lake lode. 
Subsequent movements have allowed surface waters to descend at the 
intersections of the planes of weakness determined by the lodes. The 
partial oxidation of the Tomboy and Camp Bird lodes at considerable 
depth, and the deposition within them of black oxide of manganese, 
are apparently due to fracturing of the original lode tilling, thus 
allowing the downward seepage of oxidizing waters. 
STRUCTURE OF THE LODE ORES. 
MEGASCOPICAL STRUCTURES. 
Six kinds of ore structure have been recognized in the lode ores of 
the Silverton quadrangle: 
1. Massivi structure. — The quartz, galena, sphalerite, chalcopyrite, 
