Packard— Occurrence of Copper in Western Idaho. 299 
mile and a half apart, one on the wagon road leading to the 
mines (at the White Monument hill), and the other at the Vic- 
toria mine on the northern limit of the mines where the 
mountain descends abruptly to form one side of Deep Creek 
cafion. The slightly darker appearance of the rock at the 
latter place indicates that its composition varies somewhat from 
point to point. It is also an assumption that the whole mass is 
continuous for the distance mentioned. Indeed a flow of 
basalt intervenes at one place, but the extent of the flow is 
undetermined. 
The thin sections from these specimens show that the rock 
has the following structure and composition. The structure is 
that of granite. The stout, tabular, triclinic feldspars largely 
predominate. Many of them are turbid. Interstitial quartz 
is present. The ferromagnesian minerals are hypidiomorphic, 
green, pleochroic hornblende, and some brown biotite, also 
limited by the adjoining feldspars. Apatite crystals, zircons, 
and some isometric granules of ore were also observed. A 
section from one of the inclusions described above showed 
the same mineralogical composition as the lighter-colored rock 
but the structure shows cataclastic areas. Green hornblendes, 
with inclusions, and triclinic feldspars, appear in the midst of 
the comminuted crystals. The section also shows biotite, with 
inclusions, limited by the adjoining feldspars, and the ore par- 
ticles are much more numerous than in the lighter-colored 
rock. Zonal structure of the feldspars was noticeable in both 
sections. 
The rock, therefore, as shown by these sections, is a diorite. 
Its analysis gave: 
Pete oe ees Ss "90 
ah) AS 2h: abl a IR aed asa 53°98 
pene. Ce 22 22 27°64 
2 VSS dee hh ol Poyhe need a 7°03 
aerate tule OO) ey ds 4°63 
rele (ibe fu jek eee 4°51 
0S SE OE ee On eee 1°75 
100°44 
The analysis, although only partial, is sufficient to show the 
basic character of the rock ; and the excess of soda over potash, 
together with the high percentage of lime, confirms the micro- 
scopical determination of the predominance of the soda-lime 
feldspars over orthoclase. Len 
The specimen from the Victoria mine was taken within a 
foot or two of a copper vein (bornite), and the section, viewed 
without the analyzer, shows fissures stained bluish-green by 
