58 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
mine the main lode, with a strike of about N. 40° E., is faulted by the 
Alaska lode, with an average strike of about N. 25° W. The fault 
here is apparently of the same kind as those just described — an offset 
of the northern portion of the main lode to the westward, but the 
developments in the Ridgway mine were not sufficiently extensive in 
1899 to clearly show the relations. It is interesting to find that the 
three observed cases of faulting of one lode by another are of like 
character. In each case the lode running most nearly north and 
south has been faulted by barren or low-grade lodes trending more 
nearly east and west. While the number of observations is at 
present too small to serve for the formulation of a general rule for 
the quadrangle, their unanimity is suggestive of the possibility that 
such a rule may be laid down in the future. Even now, in the event 
that a productive lode in the southeastern portion of the quadrangle 
should be found, on drifting northward, to be cutoff by a more nearly 
east-and-west lode with southerly dip, the miner, in the absence of 
other clues, is not utterly at a loss, but ma}' reasonably hope to 
regain his ore by crosscutting westward after drifting beyond the 
interruption. 
That, after the original deposition of the important ore bodies, 
there was at least one period of minor Assuring, followed by fresh 
deposition of quartz, is abundantty shown in many of the lodes of the 
region. Thus, in the Royal Tiger, the Dives, the Tom Moore, the 
Sunnyside, the Red Cloud, the Polar Star, and various other mines 
and prospects the original ore has been fissured or brecciated, and 
subsequently healed with generally barren or low-grade quartz. In 
the Tom Moore the later veinlets are notable in carrying small 
amounts of native copper in the quartz. This later fracturing is not 
always conspicuous, but small stringers of quartz, sometimes with 
rhodonite and carbonates, can usually be detected cutting the ore when 
the latter is examined in considerable masses. This is by no means 
a rare phenomenon in lodes in general, which are in most cases com- 
plex structures, resulting from successive fissurings and fillings. 
Such complexity, other conditions being the same, is more likely to 
be prominent in lodes of which the initial fractures were opened at 
an early geological period. The lodes of the Silverton quadrangle 
show much less evidence of repeated movements and filling than do 
the auriferous lodes of the Sierra Nevada, which were probably ini- 
tiated at the close of the Jurassic or in early Cretaceous time. 
Still younger than any of the fractures hitherto described are numer- 
ous fissures, usually noticeable only in mine workings in which neither 
quartz nor ore has been deposited. These are the "slips," "gouge 
seams," or "breaks" of the miners. As these names partly indicate, 
the fissures are generally filled with a wet, plastic, grayish clay, or 
gouge, which is, as a rule, merely altered and ground-up country rock, 
resulting from the attrition of the fissure walls. The presence of this 
unctuous gouge, when sharply limited by harder country rock or vein 
