QUARTZ VEINS ASSOCIATED WITH GRAVEL DEPOSITS. 



57 





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 — at least for California — that there is hardly 

 any productive quartz vein which has not some pyrites disseminated through 

 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 Avorked 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 miffht 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- 

 U1 g has ever been carried on. Some of these points may, however, be 

 discussed with more satisfaction after the presentation of the facts. 



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