172 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
Although Galena Mountain has been prospected at many points and 
has produced some ore, no important ore bodies have yet been devel- 
oped. The veins in general contain milk-white quartz and some 
barite and are apparentty not heavily mineralized. 
Antiperiodic mine. — This is a small property on the east side of 
Rocky Gulch. The lode has a general strike of about N. 38° W. and 
dips southwest about 75°. It is irregular and the ore occurs in pockets. 
The country rock is andesite. The ore consists of galena, with cerus- 
site and wire silver near the surface. Tetrahedrite, chalcopyrite, 
pyrite, and sphalerite are also present. The total product of this 
little mine during the twenty years it has been worked amounts to 
about $12,000. The ore is often of high grade, carrying sometimes 
1,100 ounces of silver and 5 ounces of gold, but it is difficult to find 
and variable in tenor. 
Ridgway mine. — This mine is situated on a spur which runs out 
northeast from Galena Mountain to Maggie Gulch. It was first worked 
in the summer of 1896 and has paid continuously. The strike of the 
lode is N. 40° E. and the dip southeast at 75°. The workings consist 
of two tunnels, with drifts and stope on the upper level. The lower 
tunnel has just cut the lode, and a winze is being sunk from the upper 
level to meet it. The countiy rock of the two main levels is massive 
andesite. The stope, however, is partly in well-bedded andesitic tuff 
about 200 feet thick, resting upon an uneven surface of the massive 
andesite. The tuff is in turn capped by an andesitic flow. The lode 
in the stope shows a maximum width of 7 feet, nearly all ore. The 
vein is "frozen" to the walls, the rock of which exhibits considerable 
alteration. The microscope shows that the andesite near the ore has 
been changed into an aggregate of quartz and sericite. The gangue 
p- of the ore is chiefly quartz, with a little calcite. Vugs are common, 
usually lined with crystals of quartz, which are sometimes faintly 
amethystine. Toward the northeast the vein, as followed in the stope, 
becomes a barren stringer lode. Toward the sou th west the ore body 
s ^ { is sharply terminated by the Alaska vein, which faults the main lode, 
apparently offsetting its southwestern continuation to the southeast. 
No ore has yet been found south of the fault, although the vein con- 
tinues beyond the offset. 
The valuable constituent of the ore consists chiefly of a dark-gray 
or black, sectile, argentiferous mineral, which contains neither arsenic 
nor antimony and is, without much doubt, argentite. Curiously, this 
mineral, with sectility as its most characteristic physical property, is 
called " brittle silver " b} T the miners. It occurs finely disseminated 
through the quartz (PI. X, A) and as small irregular crystals, with 
quartz, in the vugs. A little ruby silver is reported. There is very 
little galena in the ore, and the product of the mine is wholly in gold 
and silver. The ore shipped averages $110 per ton and carries about 
3 ounces of gold. Some of it runs much higher. In 1898, 300 tons of 
