RELATION OF ORE SHOOTS TO INTERSECTIONS. 
213 
Few examples of this rule may be derived from the Portland and Independ¬ 
ence mines. In the latter, however, the flat ore body occurring between levels 
3 and 5 may be regarded as a special case of the local expansion of ore bodies at 
the intersection of perpendicular veins with horizontal flats. 
The description of the Granite mine shows that in all cases unusual width of 
ore is associated with intersections or junctions of main lode with minor fissures. 
In the adjoining Dillon mine ore occurs chiefly in bunches at 
the intersection of sheeted zones. An example from the Dead 
Pine mine is shown in fig. 19. 
The Ajax mine is characterized by the presence of large 
and irregular bodies of replacement ore in granite. The occur¬ 
rence of these shoots is clearly related to the intersections of 
the two northeast-southwest phonolite dikes with the numerous 
northwest-southeast fissures (figs. 20 and 21). 
The Sunset-Eclipse mine, on the west side of Squaw 
Mountain, offers an illustration on a small scale. A body cf 
ore occurs here at the intersection of three fissure s}^stems. 
All these examples, the number of which could I e 
greatly increased, show clearly that deposition of tellurides 
is strongly and most favorably influenced by intersections of 
fissures. A mingling of different waters may obviously have 
occurred at such intersections and it is almost self-evident 
that such conditions might easily either excite or check the 
precipitation of certain compounds dissolved in the waters.® 
The different mingling waters may well have come from one source, although 
by traveling separate ways for a distance their character may have been sufficiently 
changed to influence the precipitation of some compound. 
o 
Scale 
50 ft 
Fig. 21. —Plan of an ore body 
in granite, level 4, Ajax 
mine, showing influence of 
contact between granite 
and breccia and phonolite 
dike in determining the 
place of ore deposition. 
OTHER FACTORS. 
A close study will soon convince one that the ore shoots directly due to inter¬ 
section are usually the smaller ones, and that although this factor is almost obtru¬ 
sively present, it is by no means the only one nor the most important. Examples 
of ore shoots apparently entirely independent of intersections would include the 
largest shoots in the camp. Among them are the Mary McKinney, Elkton, Moose, 
Vindicator, Golden Cycle, Hull City, Findley, Isabella, Portland, Stratton’s Inde¬ 
pendence, and Victor. 
It might be suggested that here, too, intersections are the cause, hut that they 
have not been observed. This, however, is improbable, for either the miner, who 
is very much on the alert for just such features, or the geologist should easily have 
recognized them. The great size of the bodies and the even distribution of the 
ore forms another argument against such a supposition. 
Wddbelieve that in these cases other causes favoring precipitation become 
operative, such as decrease of pressure and temperature, and gradual change of 
solution by diffusion, absorption, and chemical action, rather than intermingling 
a Regarding the influence of intersections, see, for instance, Van Hise, C. R., A treatise on metamorphism: Mon. U. S. 
Geol. Survey, vol. 47, 1904, pp. 1082, 1223. 
