ALASKAN MINERAL RESOURCES IN 1906. 
NIBLACK ANCHORAGE. 
The Niblack mine, on the south side of Niblack Anchorage, has been 
operated steadily throughout the year and has yielded a large produc 
tion of copper ore. 
The ore bodies occur as mineralized portions of schist bands in a 
complex consisting chiefly of greenstone schists with a few belts of 
quartz-sericite schist and allied rock types. The formation strikes 
N. 60° W., with a dip of 60°-70° SW., and is cut by several later dia- 
base dikes. Folding and faidting occur at many places and have an 
important bearing on the extent and shape of the ore bodies. De 
tailed work on these structural features in the mine has shown that 
the irregular outline of many of the ore bodies is the result of inter- 
secting fault planes. The ore is essentially low-grade chalcopyrite] 
with small values in gold and silver. Pyrite occurs in great abun- 
dance and renders the ore suitable only for smelter treatment. Small 
veinlets of nearly pure chalcopyrite are associated with ferruginous | 
quartz and constitute then the jasper ore of the miners. 
The development work for the year was as follows: Drifting and 
crosscutting, 1,670 feet; shaft sinking, 80 feet; raises and winzes, 425 
feet. The inclined shaft is now 225 feet deep and will be extended to 
a depth of 300 feet. On the 225-foot level a new ore body 90 feet long 
and 15 feet wide and following a diabase dike has been exposed. It! 
extends to the 150-foot level above, and the ore from it was being 
mined. 
IIETTA INLET. 
The mines on the west coast of Prince of Wales Island are centered 
within a small area about Copper Mountain and along the east shore of 
Hetta Inlet. A geologic sketch map of this area has already been 
published, with a description of the mines. a Briefly, the ore bodies 
are masses of chalcopyrite or carbonate ores associated with magnet- 
ite and pyrrhotite in a gangue of garnet, epidote, and calcite. As a 
rule these occur along the contact of a granitic stock, intruding beds 
of limestone and quartzite. The exceptions are the massive sulphide 
veins occurring in the greenstone schist at the Corbin and Copper City 
mines. 
Investigations on the New York and Indiana claims, the principal I 
holdings of the Alaska Copper Company, have been advanced through- 
out the year. The developments consist of several exploratory tun- 
nels at different elevations below the surface exposures of the ore 
bodies, but no noteworthy ore exposures have been made in them. 
On the north slope of Copper Mountain are the Jumbo mine work- 
ings, belonging to the Alaska Industrial Company, which are also 
upon contact deposits of chalcopyrite ore. The principal workings 
• a Bull. U. S. Geol. Survey No. 284, 1906, pp. 50-53. 
