174 ECONOMIC GEOLOOY OF SILVEKTON QUADRANGLE, [bull. 182. 
fine-grained monzonite, and the vein is a simple fissure filling, with little 
or no gouge. The workings are rather extensive, embracing three adit 
tunnels, with drifts, stopes, and crosscuts. The ore was taken down 
to the railroad on pack animals, and it is remarkable that so much 
work was done on an ore- deposit of this character without more effect- 
ive means of handling and concentrating the ore. 
Oilier lodes. — Just north of Howard sville the precipitous slopes of 
Dome Peak are traversed by several prominent lodes. There are two 
sets of these, one with a course of about N. 63° W., and the other 
about N. 25° E. They are not distinct fissures, such as would result 
from decisive faulting, but are veins showing considerable regularity 
for some distance, then branching, anastomosing with other veins or 
dying out in networks of irregular stringers. There is a tunnel, the 
name of which was not ascertained, about half a mile north of How- 
ardsville, at the junction of two of the most prominent veins. In it 
much fruitless work was done, but no extensive ore body was ever 
discovered and the mine was abandoned. The lodes, so prominent 
in the cliffs above, seemed to be pinched, barren, and irregular when 
followed under ground. 
LODES OF BURNS GULCH. 
General. — Although the lodes in this gulch were prospected at an 
early date in the history of the region and have produced some ore, 
none of them have proved permanently productive. 
Tom Moore lode. — This lode, reported to have been located in 1870, 
was being worked in 1881, and then produced a massive galena said to 
carry about 70 ounces of silver. But its development has been slow 
and intermittent. Its strike is N. 53° E. and its dip NW. 68°. The 
country rock is a rhyolitic flow breccia, part of the Silverton series. 
This, when examined at some distance from the lode, is a light-gray 
rock showing very conspicuous mottling, due to the brecciation which 
its material has undergone. Both the fragments and the matrix are 
Nttf 
essentially of rhyolitic character, although an occasional andesitic 
j3article occurs. The rock is usually streaked and spotted with little 
nests of epidote. The microscope shows that the original glassy base 
of the rock has been largely devitrified and is now a fine-grained 
granular aggregate in which quartz is the only recognizable constitu- 
ent. Phenocrysts of orthoclase and plagioclase are abundant and are 
usually partly altered to sericite. Other phenocrysts, presumably 
ferromagnesian silicates, have been changed to aggregates of quartz 
and epidote. Areas of chlorite represent what wore probably former 
phenocrysts of biotite. There is also a little calcite present. The 
accessory constituents noted are allanite and titanite. The lower 
tunnel, near the Animas River, shows an irregular stringer lead with 
a well-defined gouge slip along the foot wall. The ore shows chiefly 
galena, with sphalerite, chalcopyrite, pyrite, and sometimes tetrahej 
