DiLLEu.l COPPER DEPOSITS OF REDDING REGION, CAL. 131 
large, and what it may lead to below is an interesting question. 
Associated with the magnetite are streaks of yellowish- green garnet 
and possibly also some pyroxenes, indicating that this mass of mag- 
netite is a contact phenomenon. 
IRON MOUNTAIN DISTRICT. 
The largest and most important district of the copper region, as 
far as known at present, lies west of the Sacramento River and 
extends from Iron Mountain northeast for about 25 miles to the Sum- 
mit mine northwest of Kennett. Only one mine in the district, that 
of the Mountain Copper Company at Iron Mountain, is productive, 
although there are a number of others — for example, the Shasta King 
and the Mammoth — that are not only extensively developed, but 
rapidly approaching the productive stage. 
Iron Mountain mine. — The Iron Mountain ore bodies are marked 
upon the surface by the most prominent gossan of that region. It is 
chiefly limonite, which in the early days was mined for gold and 
silver. In places the porous gossan extends to a depth of over 100 
feet, changing abruptly from the oxides to the sulphides, but upon 
the steep slopes bordering the canyons the gossan has been denuded 
and the bodies of sulphides lie near the surface. 
In the Iron Mountain vicinity there are two principal bodies of ore; 
one, the Iron Mountain, which has been large^ mined, is said to have 
been about 800 feet long, 100 to 400 feet wide, and traced to a depth 
of r>00 feet. The other ore body, the Hornet, has a greater length, 
but less width, and has been thoroughly prospected. 
The wall rock on both sides is metarhyolite, which, according to 
Dr. W. F. Hillebrand's partial analysis, contains 5.16 per cent Na 2 
and only 0.40 per cent K 2 0, with 0.015 per cent BaO and 74.52 per 
cent Si0 2 . It is somewhat remarkable for containing so much more 
soda than potash, and appears to be related to the soda rhyolites 
described by Dr. Palache near Berkeley, Cal. 
The shear zones containing the ores strike nearly northeast and 
southwest, dipping vertically or steeply co the northwest. The ore 
bodies are elongated, flattened, lenticular in shape, and at least in 
some cases pitch in the shear zone to the northeast. 
The ores where seen in the Hornet were wholly sulphides, with the 
[Copper as chalcopyrite intimately mixed with pyrite. Chalcocite, so 
common in the dark ore at Bully Hill, was not seen in the Hornet 
| body. Sphalerite is present and occasionally forms streaks through 
the pyritous ores, giving the mass a decidedly schistose structure. 
j Whether this structure is derived from the schist which the ore is 
supposed to have replaced, or originated in the ore during or after its 
(deposition, could not be determined without more detailed investiga- 
tion. Wherever the schistose structure was observed it was generally 
[parallel to that of the adjacent schistose igneous rock, but some of 
