58 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bi^l. 313. 
"The Dahlonega Consolidated Gold Mining Company's plant," by 
W. Colvin, August 17, 1901; "The Crown Mountain gold mine and 
mill," by H. V. Maxwell, September 21, 1901, and "Gold dredging in 
north Georgia," by the same author, November 2, 1901. 
GENERAL GEOLOGY. 
All the rocks of the Dahlonega district of Lumpkin County, Ga., 
are highly crystalline, no series of indisputably sedimentary origin 
occurring in the immediate vicinity. The rocks dip usually at a 
high angle to the east. The strike is, in general, about N. 60° E., 
but at the northern end of Findley Ridge this changes abruptly to 
N. 5° W. In consequence of this change of strike the mines, as 
would be shown on a mine map of the district, occur along two lines 
meeting almost at a right angle. Four rock types occurring in the 
district are sufficiently well marked and areally important to be 
separately described. 
Mica-schists. — For convenience (ho normal rocks of the district 
(excluding the doubtful feldspathic gneisses next described, and the 
granites and diorite, which are undoubtedly of igneous origin) will 
be grouped as mica-schists. More fresh material than is at present 
available must be examined before finer distinctions can be profitably 
made. 
Though the decomposed outcrops seem, in general, to be highly 
micaceous, examination of fresh material from several mine tunnels 
seems to show that these "mica-schists" are prevailingly siliceous, 
the mica being highly developed only along joint and shearing planes. 
This highly siliceous character would seem to point toward a possible 
sedimentary origin of at least part of these schists by metamorphism 
from impure sandstones. This question, however, requires much 
further investigation. 
As to age, nothing occurs in the district which can be used as proof 
of the absolute age of these rocks. Lacking such proof, they have 
been generally regarded as pre-Cambrian, but possibly they are of 
Cambrian or Lower Silurian age. As to relative age, it is certain that 
they are the oldest rocks of the immediate district, with the possible 
exception of certain feldspathic gneisses, which are next described 
Feldspathic gneisses. — At several points in the area under consid- 
eration highly feldspathic gneisses occur, notably in one northeast- 
southwest trending ridge, parallel to and some miles east of the 
Chestatee River. These rocks are well banded, some bands consist- 
ing largely of mica and quartz, while others contain much feldspar. 
It is possible that these feldspathic gneisses constitute a true rock 
type, but at present the writer is inclined to believe that the more 
feldspathic bands simply represent granitic material injected into a 
preexisting mica-schist and subsequently sheared with it. In some oi 
the larger bands of feldspathic material this derivation from granite 
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