196 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182, 
Bonanza mine. — In 1879 this mine was opened on the north side of 
Lake Como, through a tunnel 250 feet in length, and is said to have 
produced an ore carrying gray copper (tetrahedrite) and barite. In 
1881 it was reported that 700 tons of tetrahedrite and galena ore had 
been extracted and piled on the dump, and in 1883 some 700 feet of 
development work had been accomplished. The lode was also 
exploited by a small shaft near the edge of Lake Como. No great 
amount was produced and the property has been idle since 1890. The 
ore seen on the dump in 1899 showed galena, sphalerite, pyrite, chal- 
copyrite, and tetrahedrite, in a gangue of quartz, barite, and a little 
rhodonite. The tetrahedrite appeared to be closely associated with 
the barite. The ore shipped is reported to have carried from 40 to 45 
ounces of silver. There are several other idle prospects about the 
lake, but they present no features meriting special description. A 
project was at one time set on foot to drain the lake by a tunnel, in 
order to secure the rich "float "which it was supposed would be 
found in its bottom. Fortunately for the projectors and for the lovers 
of the picturesque, this scheme fell through. 
Other mines and prospects. — The Red Rogers claim is on a very 
prominent lode just southwest of Lake Como and crossed by the 
trail from the lake to Cement Creek. This property, which was well 
known in the early eighties, has been idle for some years. It was 
developed by surface cuts and one or more small tunnels, and proba- 
bly never produced much paying ore. The course of the lode is N. 
43° E., w r ith nearly vertical dip. It is the most westerly of the numer- 
ous large lodes that converge from the south toward the lake. It 
does not appear to reach the latter, however, as it curves strongly 
eastward just north of the Red Rogers cabin (which is on the crop- 
pings), and joins the Seven Thirty lode. The Seven Thirty lode is 
one of the strongest and most persistent lodes of this region. Its 
course is about N. 85° E. The dip is approximately vertical. Toward 
the west the lode passes over the ridge into Grey Copper Gulch. 
LODES OF THE UNCOMPAHGRE CANYON. 
General. — The Uncomphagre River, below the mouth of Pough- 
keepsie Gulch, has cut the greater part of its picturesque gorge deep 
into the Algonkian schists. The San Juan andesitic breccias rest 
upon the uneven eroded surface of these schists, slates, and quartz- 
ites, and tower in lofty cliffs above the river. These cliffs are trav- 
ersed by fractures and veins, which are particularly conspicuous 
when they cut the San Juan breccias. The cliff faces of the latter 
are sometimes directly due to the falling away of great masses of 
rock along one of these fracture planes. Some of the fractures carry 
ore, and have been worked with varying success. 
Michael Breen mine. — This mine, more familiarly known as the 
Micky Breen, is on a small, nearly east-and-west lode (N. 85 c W.1 
