80 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
friction breccia in which the angular fragments of black shale are 
inclosed in a matrix of quartz and calcite. The quartz shows radial 
crystallization outward from the separated fragments, and often open 
spaces remain into whicli the small crystals of quartz project. The 
walls of such veins are sometimes sharply defined, but in other cases 
many small veins of quartz traverse the shattered wall rock in every 
direction, so as to render it difficult to draw the limits of the vein 
itself. This transition from the peculiar type of vein into the shat- 
tered rock shows the "bird's-eye" quartz to be due to brecciation 
along more or less well-defined zones, followed by mineralization. 
The "bird's-eye" quartz has its gold content very irregularly dis- 
tributed. The values are mostly in free gold, with a small amount of 
sulphurets present. The gold occurs in fine grains within the quartz or 
next to the included shale fragments, and the approximate value of 
the ore may be readily found by panning, while in many cases the gold 
may be seen on the surface of the quartz, in the form of incrustations 
of leaf or wire gold. In a specimen from the Gold Leaf mine per- 
fect octahedral crystals of gold lie upon the ends of the quartz crys- 
tals. The silicification sometimes extends into the county rock, and 
some values are found there. The gold of the quartz veins, like that 
of the gravels, is Light colored and contains a considerable percentage 
of silver. In the Little York this silver is reported as amounting to 
about 20 per cent. 
The quartz veins that have been opened np in the upper basin of 
Williams Creek have a general uortheast trend, being thus roughly 
parallel with the basalt dikes. In the Cougar the hanging wall of 
the vein appears to be a badly decomposed basalt dike, while in the 
Gold Leal' one vein is wholly in sandstone and shale and another in a 
large diabase dike. The relation of the veins to the dikes is there- 
fore not const ant, but it may be noted that the fractures which have 
been filled by the vein material are usually approximately parallel to 
the fractures in the vicinity which have been filled by the intrusion 
of basalt. That there has been more than one period of fracturing, 
and that the period of mineralization was not exactly contempora- 
neous with the time of igneous intrusion, is shown by the occurrence 
of veins cutting the dikes themselves. It is quite probable, however, 
that the two processes occurred within the same geologic period and 
that the ore-bearing solutions derived their heat, and possibly their 
mineral content, from the intrusive and eruptive basalt of the area] 
A number of quartz veins on Swauk, Williams, Boulder, and Baker 
creeks are being prospected at the present time, and in view of the 
richness of the alluvial gold which has been derived from the veins 
in this vicinity it would seem that the prospecting is well warranted. 
