68 
ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182 
safeguard against such mishaps and is the prerequisite of all intelli- 
gent and extensive prospecting. 
As a rule the country rock adjoining the veins is not strikingly 
altered and retains practically the original form of the fractured sur- 
faces. In some veins in rhyolite, however, there has been some 
replacement of the rock by ore, as may be seen in the Tom Moore 
mine. 
Veins of the simple type described are connected by many transi- 
tional forms with lodes occupying closely spaced sheeted zones and 
consisting really of several parallel veins. Such are the small lodes 
of the Micky Breen and the important lodes of the Camp Bird and 
Tomboy mines. In both the Camp Bird and Tomboj^, however, the 
parallel veining resulting from sheeting of the country rock is asso- 
Feet 
Fig. 4.— Sketch section of the Silver Crown lode, showing stringer-lode structure, a, andesite; 
6, quartz; c, andesite and quartz stringers; d, ore. 
ciated with the less regular linked-vein structure, in which the lode is 
made up of nearly parallel or slightly diverging veins connected by 
linking stringers (Trummer) and with the yet more irregular stringer- 
lode structure, in which the lode consists of a mass of stringers with- 
out noticeable parallelism among themselves. In these mines the 
more regular structure is usually found with the gold ore separated 
from the hanging wall by a little gouge, while the more irregular 
structures characterize the foot- wall portion of the lode, carrying a 
low-grade galena ore and sending off irregular stringers into the 
country rock, and being thus without regular foot Avail. 
The stringer-lode structure is perhaps best exemplified in the North 
Star (Solomon) lode, in portions of the Royal Tiger and of the Pride 
of the West lodes, in the upper part of the Forest lode, and in the 
Alabama lode. But it inaj^ frequently be well studied in surface out- 
