Cr 
~l 
QUARTZ VEINS ASSOCIATED WITH GRAVEL DEPOSITS. 
more than traces of the other minerals mentioned. It is also true that 
auriferous quartz veins rarely contain any large amount of the ores of the 
other metals, with the exception of iron. Pyrites, or the common bi-sulphuret 
of iron, is a very common associate of gold in the quartz veins; so common, 
indeed, that it may be said 
any productive quartz vein which has not some pyrites disseminated through 
at least for California — that there is hardly 
it; yet the quantity of the latter is usually small, as compared with that of 
the quartz. It is also true, that the pyrites almost always contains gold ; and 
that in the great majority of instances it is richer in gold than the quartz 
itself. Furthermore, it may be added that the other common sulphurets, 
those of lead and zinc, are also frequently present in productive quartz veins, 
although never, so far as observed in California, in large amount. It is con- 
sidered a good “ indication” — that is, a sign of probable richness in gold — 
when the vein has disseminated through it, in small particles, more or less of 
iron and copper pyrites, blende, or galena. 
With these preliminary remarks in regard to the mineralogical character 
of quartz veins, we may proceed to add a few words about their association 
with the auriferous gravels in the Sierra. In general the geographical range 
of the gravels is much more extensive than that of the quartz veins, at least 
of such as are productive. It is true, however, that so large a portion of the 
bed-rock is covered by gravel and volcanic materials, that it is not easy to 
say where quartz veins do, or do not, exist. From the very nature of the case, 
if we suppose the quartz veins to be equally distributed through the bed- 
rock, there would be more of them discovered and worked when this was not 
covered by the detrital masses, which, except when artificially removed by 
mining operations, would effectually conceal the surface, and prevent finding 
of such veins as might exist. That the auriferous gravels should be found on 
the slope of the Sierra in positions lower than the region where quartz veins 
occur is what might naturally be expected, gravitation, aided by currents of 
water, continually impelling the auriferous particles downward. But there 
are also considerable deposits of gravel in positions higher up in the range 
than where quartz veins could be expected to be found; or, at least, higher 
than any even moderately productive ones have been. Here many beds of 
streams, especially in the southern Sierra, seem to have been worked over— 
and apparently with profit— in regions where no remunerative quartz min- 
ing has ever been carried on. Some of these points may, however, be 
discussed with more satisfaction after the presentation of the facts. 
