378 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
MODOC MINE. 
PRODUCTION AND DEVELOPMENT. 
• 
The Modoc mine, on the Ocean View claim, is owned by the Modoc Mining 
and Milling Company, and is situated a few hundred feet south of the Last Dollar, 
on the eastern slope of the broad gap separating Bull Hill from Battle Mountain. 
The property has been worked constantly since 1897 and has been a steady pro¬ 
ducer and dividend payer. Efforts to ascertain the total production have failed, 
but the mine has probably yielded approximately half a million dollars. 
The shaft, which is situated near the north end of the claim, is vertical for the 
first 110 feet and then changes to a steep incline down to level 11, a total vertical 
depth of 675 feet. From level 11a winze 400 feet deep extends down to level 15, 
which at present is the deepest. The elevation of the collar is about 10,150 feet, 
and the total depth 1,075 feet. Developments aggregate about 6,000 feet. Levels 
7 and 9 extend practically through the entire claim, while those above and below 
are confined to the north end, except level 15, which is 800 feet long. At present 
(1904) work was carried on only from level 9. The mine has no water in the bottom, 
but gas fills the winze 200 feet and sometimes 400 feet deep. 
GEOLOGICAL FEATURES. 
- The syenite area of the Last Dollar mine changes to breccia near the north 
end line of the Modoc property, and breccia continues as the principal country 
rock until the southern part of the claim is reached. The rock is of normal appear¬ 
ance and often contains much phonolite, but on the bottom level it is said to be 
loose and sandy, with open caves in places. A phonolite dike not more than 20 
feet thick has been followed for 300 feet on level 9, 600 feet south of the shaft. A 
large and irregular mass of the same rock appears on the same level 200 feet farther 
south; it seems to be about 100 feet wide and extends at least 148 feet below level 
9; possibly it is connected with the first-mentioned dike. The southern face of 
level 9 is in breccia. 
VEIN SYSTEM. 
The Modoc vein Xo. 1 is followed underground for 1,300 feet, almost from one 
end of the claim to the other. It is a narrow sheeted zone about 4 feet wide; the 
foot-wall seam is usually well defined, as is sometimes also a hanging-wall seam. 
Where the vein traverses phonolite, it seems less sharply defined, but the ore widens 
considerablv. The vein curves slightlv eastward, so that while at the north end 
the strike is X. 20° W. it has changed to X. 10° E. in the southern part of the prop¬ 
erty. The dip is constantly 75° to 80° W. A shorter and parallel vein called Xo. 
2 is opened on the east side near the shaft on level 9 and on several of the upper 
levels. Many short seams cross the main vein, trending northeasterly near the 
shaft and southeasterly in the southern part of the claim. Xo faulting was observed 
at the intersections. A distinct but barren vein follows the first phonolite dike, 
600 feet south of the shaft; its strike is northwest, its dip 70° XE. 
