304 ~—-B. Silliman on the Mining Districts of Arizona. 
are of little value compared to the actual reduction of large 
quantities of the ores in working processes. 
Other lodes of this distric.—My notes contain mention of over 
fifty lodes or veins, most of them probably distinct, which I 
visited in the course of my explorations of the San Francisco 
distfict, and which belong to the east-and-west system. The 
parallelism between the lodes of this system is almost exact, and 
there is a great similarity in their mineralogical character. 
The ‘Skinner,’ on the south side of Silver Creek, is one of 
the most conspicuous, forming like the Moss lode bold and fan- 
tastic crests, rising sometimes in slender needles to a remarkable 
height. he boldest outcrop is called the*“center claim,” of 
1600 feet. But those portions called the Rochester (1800 feet) 
and the San Francisco (2400 feet) are nearly as bold. This lode 
shows drusy quartz, both compact and cellular and ferruginous 
with numerous cavities where fluor-spar has been weathered out. 
Hornstone is also seen frequently. Very small traces of sulphids 
show at surface, which is much stained by black oxyd of man- 
ganese, rendering portions of the outcrop quite black. 
This vein varies from 50 to 150 feet in thickness. Its walls 
of ash-colored feldspathic porphyry are seen in places beautifully 
polished on the line of the dip 70° It appears glued first to 
the porphyry, without a lining of clay, (fluccan), but this 1s $0 
commonly the case in the outcrops of Nevada that it is no proo 
of the absence of this important character of a true vein ata 
moderate depth. ‘ 
An exploratory shaft has been sunk near the center of this 
claim on the foot wall, ata point designed to cut the lode at the 
depth of 100 feet, but at a depth of 50 feet the resources of the 
explorer gave out. LHighteen feet of water in this shaft confined 
occasional gray spots of minutely diffused sulphid of silver. 
Three assays of the ore from this shaft proved the presence of 
silver to the value respectively of $25, $74, and $83 to the ton 
of 2000 lbs. From a second shaft sunk on the N.E. side of the 
wash, in the body of the vein, to a depth of 25 or 30 feet, I ob- 
tained beautiful octahedral crystals of green, white, and purple 
e 
