ransome.] LODES OF BURNS GULCH. 175 
drite, in a quartz gangue. A little rhodochrosite occurs in vugs. The 
country rock alongside the lode is impregnated with pyrite and specks 
of* galena to a greater extent than is usually observed in this region. 
When examined in thin section under the microscope, it is seen to be 
altered to an aggregate of quartz, sericite, and ore, traversed by vein- 
lets of quartz. The original brecciated structure and the outlines of 
many of the feldspar phenocrysts have been preserved in spite of 
complete recrystallization. The feldspars have usually been altered 
to aggregates of sericite. 
A second tunnel, several hundred feet above the lowest opening, 
was not accessible. The dump, however, showed that this portion of 
the lod<- was originally a breccia zone in the rhyolite which became 
filled with ore, accompanied by considerable impregnation and 
replacement of the country rock. This ore deposit was itself shat- 
tered and veined with white quartz, carrying little or no ore. 
The upper tunnel, 200 feet above the last, was being worked on a 
small scale in 1808. The ore streak here is frozen to the walls and 
carries no quartz save in some small later stringers, often accom- 
panied by kaolin, which cut the ore, and in a few drusy vugs, where 
it is sometimes accompanied by a little pale-lilac fluorite. The ore 
is chiefly tetrahedrite, with some chalcopyrite and galena. Sphaler- 
ite was not seen. There is said to be some bismuth present, probably 
as a sulphobismuthite of lend, and the occurrence of hiibnerite was 
noted in small crystals in the later quartz stringers. The width of 
the lode is usually from .*i to 6 feet, and it is in part a replacement of 
the rhyolitic walls. The chalcopyrite occurs chiefly in the middle 
portions of the ore- stringers. The tetrahedrite on each side of io is 
solid for a short distance and then fades off into the altered country 
rock as minute veinlets and specks associated with chalcopyrite or 
pyrite. Such gangue as is present with the ore is altered rhyolitic 
flow breccia, consist ing chiefly of finely crystalline quartz and sericite. 
The lode is thus not sharply differentiated from the country rock on 
each side of it. The tetrahedrite is not highly argentiferous. The 
first-class ore runs about $60 to the ton and the second-class about 
$48. The chief value is in copper, but there is some silver and a lit- 
tle gold, the last sometimes in visible particles. Free copper is not 
uncommon in these upper workings, but is confined, as far as is known, 
to the small stringers of younger white quartz which cut the ore. 
These sometimes show comb structure, and the copper occurs along 
with the medial suture of the stringers. 
The middle tunnel is said to have furnished ore carrying more 
galena and higher in silver, with subordinate amounts of tetrahedrite, 
while in the lowest tunnel tetrahedrite was rare. 
Silver Wing mine. — This property comprises several lodes, of which 
one is the northeast extension of the Tom Moore. Some development 
of these lodes was in progress as early as 1880, but they have never 
