MINES OF GOLD HILL. 
309 
GEOLOGICAL FEATURES. 
The prevailing country rock of the Anaconda mine is breccia of the usual type 
found on Gold Hill. Within this breccia are some irregular bodies of latite-phonolite 
and a few dikes of phonolite and ‘‘basalt.” In the northern part of the adit level 
is exposed the same mass of schist that outcrops as an isolated area in the breccia 
at Fairview, on the northeast side of Gold Hill. The general distribution of the 
various rocks, so far as it lias been ascertained, is shown in fig. 30, a plan of the 
adit level. The latite-phonolite is probably intrusive into the breccia, but, as is 
so frequently the case in this district, the contacts are too indistinct to furnish 
decisive evidence on this point. A small phonolite dike sometimes accompanies 
the Anaconda lode, but is not a constant feature. There are two important basic 
•intrusions in the mine. One of these is exposed at three points on the adit level 
in the vicinity of the Excelsior shaft (fig. 30). It is apparently a rolling, irregular 
sill with a general dip of about 20°. Near the Excelsior lode the dip is easterly, 
but farther south, where the “basalt” is cut by the Anaconda lode, the dip is 
southerly. The same sill is cut on level 8, 200 feet below the adit. It seems to be 
generally parallel with the Howard “basalt” sill, but to lie from 200 to 300 feet 
vertically below the latter. If so, it may be cut in the Mary McKinney mine when 
level 6 is extended north. The other basic intrusion is a north-south dike in breccia, 
in the Colorado Boss ground. There is also a small basic dike in the breccia north 
of the syenite-porphyry mass, but it has been exposed for only a short distance. 
LODE SYSTEMS. 
The principal lodes exposed in the Anaconda mine are the Anaconda, Virginia 
M. or Lincoln, Howard Flat, Work, Excelsior, Colorado Boss, and Kittle M. or Matoa. 
They are all shown in fig. 30. 
The Anaconda lode strikes from north to X. 5° E. and dips 70° E. On the 
south, although the lode shows a tendency to split up into a number of irregular 
fissures, the general zone of Assuring probably continues into the Mary McKinney 
as the No. 2 lode. Toward the north the Anaconda on the adit level retains its 
regular course until it meets the Excelsior lode (fig. 30). The Anaconda is com¬ 
monly supposed to turn at this junction and run northeast, following in part the 
contact between the latite-phonolite and the breccia. Whether it does so or whether 
the northeast lode is a different fissure zone could not be satisfactorily determined, 
owing to the number of subordinate fissures at the junction of the Anaconda and 
Excelsior lodes. No north-south lode corresponding to the Anaconda is known, 
however, north of the Excelsior lode. In the northern part of level 10, which 
could not be visited on account of impure air, the Anaconda lode apparently curves 
to. the east before it reaches the Excelsior lode. ' 
The Excelsior lode for about 450 feet east from the Anaconda lode strikes X. 
80° E. It then turns about 20° to the south and soon becomes indistinct. West 
of the Anaconda lode the Excelsior is practically unknown. It dips about 60° N. 
The Excelsior and Anaconda lodes pass at their junction into a plexus of fissures 
within which it is impossible to determine the exact relation of one lode to the other. 
The Colorado Boss lode, worked by lessees through the Anaconda adit, is a 
