STRUCTURE OF THE GOLD DEPOSIT*. 
157 
half a mile in length. Lodes of approximately this length are the Mary McKinney, 
Doctor-Jackpot, and Buena Vista. Some of the broader zones of nearly parallel, 
linked, or imbricated fissures are, however, traceable for over a mile. 
Many of the most productive fissure zones are remarkably short. The so-called 
Captain system in the Portland min#, for example, in which the fissures, while 
collectively rich, are at best individually small and inconspicuous, contains few 
lodes that can be traced for over 300 feet. Cross cuts have more than once passed 
within a few feet of ore bodies 50 or more feet in width which were discovered only 
by subsequent exploration. In such broad zones of individually nonpersistent 
fissures there is often great difficulty in identifying veins crosscut at levels 100 feet 
apart, without actually stoping them. This is especially the case in the Portland, 
Stratton’s Independence, and Vindicator mines. The productive veins in the 
granite of the Ajax mine, southwest of the shaft, are probably all less than 500 feet 
in length. In the Anchoria-Leland mine some fissure zones which are very regular 
for short distances dwindle in a few hundred feet to a single indistinct crack or come 
to an end at the junction with another fissure zone of different strike and dip. In 
the Last Dollar mine the main system of parallel fissures is crossed by east-west 
cross veins which can be followed only for short distances. 
Information concerning the persistence of fissures in depth is even less satis¬ 
factory than that relating to length, as in many cases it is impossible to discriminate 
clearly between depth of pay shoots and depth of Assuring. The ore and the fissure 
zone are not necessarily coextensive, though often little is known of the extension 
of the fissures below the bottom of an ore shoot. 
In general the persistence of a fissure down the dip seems to be roughly pro¬ 
portional to the length of the fissure. The long fissures, such as those of the Elkton 
and Mary McKinney lodes, can probably be followed far below the present bottoms 
of the mines. Many of the shorter fissures, however, are known to die out at 
moderate depth and are often succeeded by overlapping parallel fissures of similar 
character. 
These relations are well illustrated in the Portland mine. The No. 1 Hidden 
Treasure vein was first recognized on the 350-foot level and was productive down 
to level 9. If the fissure zone continues to level 10, it is very inconspicuous. The 
No. 2 Hidden Treasure has been productive from level 6 to level 8. The No. 3 
Hidden Treasure is not known above level 6, although at the bottom of the mine 
it is the only lode of the group which was known at the time of visit. The short 
lodes of the Captain group are of little importance above the 220-foot level, attain 
their maximum development near the 350-foot and 500-foot levels, and become 
very indistinct on level 7, although there are still traces of this group of fissures on 
level 10. Within the group individual fissures, or narrow zones of fissures, die out 
and overlap as do the Hidden Treasure lodes. The No. 4 Lee, on the other hand, 
though not a long lode, is unusually persistent in depth, being known on practically 
all the levels of the Portland mine. The Diamond vein, a fissure zone in granite in 
the same mine, is not known above level 5. Its fissures are unproductive, though 
distinct, on level 10. The Portland vein becomes very indistinct below level 6 
and on the lower levels is unknown. 
13001—No. 54—0& 
12 
