STRUCTURE OF THE GOLD DEPOSITS. 
161 
of tlie district, finds partial exemplification in the No. 1 Lee vein of the Portland 
mine. 
Among the numerous and important lodes coming properly under the desig¬ 
nation of sheeted zone, several structural varieties can be distinguished and are 
sometimes exhibited in different parts of the same lode. A common form is that 
Fig. 6.—Veins in Last Dollar mine. 1. Main vein, 40 feet above level 12. Typical sheeted and partly brecciated zone in fresh 
iatite-phonolite. Seams coated with quartz, dolomite, and calaverite. 2. Cross veins with medial vug holes, level 10. 
3. Vein, west drift, main cross vein, level 5, showing middle filled fluorite vein. 4. Cross vein No. 3, at east side line, level 5. 
characterized by the presence of two main parallel fissures, usually 3 or 4 feet apart, 
accompanied by less regular and less persistent fractures in the intervening and 
adjacent rock. As an example of this type may be cited the Legal Tender vein, in 
breccia, as seen on level 10 of the 
Golden Cycle (fig. 5), and the 
Doctor-Jackpot vein, also in 
breccia. The Gold Coin vein 
and A, B, and C veins of the 
Ajax mine show a similar struc¬ 
ture in the granite. 
In another common type of 
sheeted zone the parallel fissures 
are more numerous, and are 
spaced with some regularity, as 
illustrated in fig. 6. There is 
usually a medial portion of the 
lode, ranging from a few inches 
to a foot or two in width, within 
which the rock is divided into a 
large number of very thin plates 
by fissures often less than an 
inch apart. This band of in¬ 
tense sheeting is accompanied on 
both sides by parallel fissures 
which are spaced farther and farther apart, so that the sheeted zone as a whole 
merges gradually into the country rock. This type is well exemplified by the 
Howard fiat vein, in the southern part of the adit level of the Anaconda mine (fig. 7). 
10 
20feet 
i 
Fig. 7.—Structure of Howard flat vein, Anaconda mine, adit level. 
Illustrates close sheeting in middle part of vein, the fissures becom¬ 
ing gradually farther apart in the foot and hanging walls. 
