198 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
VEIN OXIDATION. 
In a very general way the depth of oxidation of the veins coincides with the 
depth of the water level, but here again there are numerous exceptions and quali¬ 
fications to be noted. Fresh tellurides often occur high above the water level, 
especially in hard and massive rocks. On the other hand, partial oxidation is in 
many cases apt to extend for several hundred feet below that level. 
At the Abe Lincoln and Beacon Hill mines unaltered tellurides appeared 
practically at the surface, as woidd be expected from the high stand of the water 
level at these mines, the elevations of which are 9,611 and 9,370 feet. But the 
same applied to the Gold King and C. O. D. mines, high up in Poverty Gulch, with 
elevations of about 9,850 feet. At the Moon-Anchor mine, on Gold Hill, oxidized 
ore extended down to the 600-foot level, or to an elevation of 9,200 feet. At the 
Doctor-Jackpot mine oxidation reached only a short distance below the surface 
in the Jackpot vein, while in the Doctor vein the ores were oxidized down to a depth 
of 650 feet below the surface, or an elevation of 9,078 feet. 
On Bull Hill the water level should lie about 700 feet below the surface, or at 
an elevation of 9,600 feet, although no accurate observations are available because 
the region was drained by tunnels long before the shaft had attained its depth. 
At many of the small mines on this hill tellurides were, however, met much higher 
than 700 feet. The Zenobia vein is entirely oxidized down to a depth of 500 feet. 
In the Last Dollar the veins are entirely oxidized above the 800-foot level, or 
above an elevation of 9,600 feet. Below this unaltered tellurides form the ore. 
The adjoining Modoc mine contains in places oxidized ore down to a depth of 
1,000 feet, although some tellurides were found on level 2. The Gold Sovereign 
mine shows partial oxidation to at least 550 feet, and on that level one-half of the 
Lovett vein is almost fresh, while the other half is entirely oxidized. 
The water level of the Isabella mine was probably 900 feet deep (elevation 
9,557) and complete oxidation of the veins certainly reached that depth in the 
breccia, partial oxidation being noted at least 100 feet lower. But in the latite- 
phonolite of the Buena Vista incline, on the same vein, tellurides were found on 
level 2 and on the lower levels the vein is scarcely attacked by oxidation. 
On the south slope of Bull Cliff both water level and vein oxidation are deep. 
At the Hull City mine partial oxidation reaches down to 850 feet below the sur¬ 
face, while the original water level is reported as being only 516 feet deep. At the 
Vindicator mine the first water was found at 500 feet, or at an elevation of 9,700 feet. 
All veins are oxidized down to this level, and to some extent even down to the 
800-foot level. The country rock is chiefly massive latite-phonolite. In the Golden 
Cycle mine, where breccia predominates as country rock, energetic oxidation has 
penetrated to unusual depths. The natural water level is unknown, but was, at 
any rate, less than 800 feet below the collar. The surface elevation is 10,066 feet, 
and the original water level may be tentatively given as at 9,500 feet, or 566 feet 
below the surface. Vein oxidation goes, however, much deeper than this, for 
between the 800- and 900-foot levels the veins are almost completely oxidized; a 
small amount of tellurides is, however, found in many places. The deepest level, 
1,000 feet below the surface, was under water at the time of visit. 
