166 ECONOMIC GEOLOGY OF SILVEKTON QUADRANGLE, [bull. 182. 
are perhaps connected with the Potomac lode, which is known to 
carry barite, and should join the North Star lode from the north at 
about this point. Barite was not recognized in the ore of the North 
Star mine. 
The country rock of the Dives is that of the North Star. It shows 
some alteration close to the ore bodies, being bleached in color, trav- 
ersed by veinlets of quartz, and full of minute cubical crystals of 
pyrite and occasionally specks of galena. The microscope shows that 
it has undergone entire metasomatic recrystallization and consists 
chiefly of quartz, serieite, and pyrite. 
The Dives was worked on a lease in 1899, the ore being treated in 
the North Star (Crooke) mill. In 1900 it was idle. 
The Mountaineer and Lookout mines have not proved steadily pro- 
ductive claims, although in the Mint report for 1891 the Lookout is 
credited with a production of $27,152. Both are now idle. The tun- 
nel of the latter is run in Algonkian schists, just beneath their con- 
tact with the overlying volcanic rocks of the San Juan series. The 
schists are shattered and decomposed, and the deposit appears to be 
very bunchy and irregular. The ore shows galena, chalcopyrite, and 
pyrite. The Mountaineer is said to have been located by prospectors 
from New Mexico in 1870. At least three veins can be seen cropping 
in the steep bluffs of San Juan breccia above the Lookout tunnel, and 
apparently converging just south of the tunnel mouth in what is 
locally termed a "blow-out." This is a mass of shattered limestone 
(probably the Ouray limestone (Devonian), which overlies unconform- 
ably the Algonkian schists south of the Highland Mary mine) and 
fragments of schist and andesite, cemented by comminuted andesitic 
material. Some of the limestone fragments are surrounded by envel- 
opes of hematite. The whole mass is somewhat mineralized and is 
$*! traversed by quartz stringers. The origin of this area of local dis- 
Hi turbance is not certainly known. The original shattering may have 
^*! been due to the movements which formed the veins that converge at 
this point. There has, however, been some recent movement of a land- 
slip character, which has tended to obscure the original relationships. 
Big Giant lode and others. — In Big Giant Gulch are several lodes 
which m&y be conveniently described in connection with the North 
Star lode. The most important of these is the one on which the 
Potomac claim is located. Some work has been done on this claim, 
and also on the Big Giant, which appears to be on the same lode. 
On the latter claim the lode is apparently a stringer lead, without 
any considerable gouge and carrying much chalcopyrite in its ore. 
It dips southwest at from 75° to 80°. A small mill was erected on 
this claim, but the mine was not successful, and was idle in 1899. 
Toward the southeast this lode passes over the northern shoulder of 
Big Giant Peak and is supposed to join the North Star vein in the 
Dives claim. There are other lodes in this gulch, two of which are 
shown on the map, but they have not proved to possess any value. 
IU 
