124 THE GOLD DEPOSITS OF DAHLONEGA, GA. 
garnet, as already indicated by Becker, contains native gold. At other mines the altera- 
tion of the mica schist is not extensive, though the rocks next to the vein may acquire a 
more silvery luster, due to some additional development of muscovite in the schist. The 
biotite in the schist remains unaltered, as does the chlorite and feldspar. Crystals of garnet 
may develop in the schists near the vein. Chalcopyrite, pyrite, and pyrrhotite, probably 
due to vein-forming action, appear in small quantities in the wall rock, but with these mag- 
netite or ilmenite may be associated. 
As observed in the Benning vein, the alteration of the granite adjoining the veins is very 
slight, being limited to a slight development of chlorite along the contact. In the Jumbo 
mine, on the other hand, the mica schist has been altered next to the quartz seams; seri- 
cite has evidently developed at the expense of biotite, which is practically eliminated. 
Nor is there any magnetite or ilmenite in the altered rock, though much pyrite and rutile 
have developed. 
All this seems to show that the veins of Dahlonega were not all formed under the same 
conditions. There are, on one hand, the prevailing veins like the Standard, Lockhart, and 
many others in which, during the vein-forming processes, biotite, hornblende, garnet, epi- 
dote, spinel, magnetite, and ilmenite were stable compounds. These again may be divided 
into those carrying garnets, like the Lockhart, Findley, and McAfee veins, and others in 
•which garnet is absent, like the Benning or the Standard. On the other hand, in the Jumbo 
mine biotite and magnetite appear to be unstable under the influence of vein-forming 
solutions. 
The association of minerals and the metasomatic alteration in the first of these two classes 
is very different from that prevailing in the California gold-quartz veins and in fact in all the 
principal classes of gold and silver veins of the West. 
In these California veins magnetite, garnet, ilmenite, spinel, hornblende, and apatite are 
practically unknown as vein minerals. In the alteration by the vein solutions magnetite, 
feldspars, biotite, hornblende, and epidote are unstable and are converted to a fine-grained 
aggregate of sericite with quartz or carbonates, as has taken place in the Jumbo mine. In 
the prevailing class of Dahlonega mines, on the other hand, the products of alteration are 
such minerals as occur in areas of regional metamorphism or in contact zones, and yet the 
association of quartz and some calcite with native gold and pyrite, chalcopyrite, and zinc 
blende is unmistakably similar to that of the California veins. It may be permissible to 
conclude from this that the solutions in both cases were similar, but that they acted under 
different physical conditions. The temperatures prevailing during the deposition of the 
southern veins were probably much higher than those in the Cordilleran region at the levels 
now accessible to us in mineral deposits there exploited. Becker justly remarks that the 
southern veins have been subjected to long-continued erosion and that the present croppings 
are far below the original ones, possibly as much as 15,000 or 20,000 feet. On the other 
hand, in the western mines, the amount of rock removed undoubtedly falls far short of this 
amount. 
If this conclusion is correct, it is evident that the precipitation of gold from vein-forming 
solutions extends over a very large vertical range. In California this range is known to be 
at least 3,000 feet a At Bendigo, Victoria, mining has reached a depth of 4,000 feet, and at 
least 2,000 feet of rock have been removed by erosion. The veins still bear the general char- 
acter of the California gold-quartz deposits. 
It is scarcely to be expected that a brief investigation like the present one should yield 
any definite clews as to origin of the gold. The clustering of the veins about intrusive 
masses of granitic rocks is, however, a very suggestive fact which previous investigations of 
Dahlonega mines have not sufficiently emphasized and which is repeated in practically all 
known occurrences of typical gold-quartz veins. The probable great depth of deposition 
would also suggest that circulation of surface waters was a negligible factor, although it is 
conceded that the plasticity of the rocks was not so great as to preclude the existence of 
aLindgren, W., Gold-quartz veins of Nevada Citv and Grass Valley districts, California: Seven- 
teenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1896, p.*183. 
