120 THE GOLD DEPOSITS OF DAHLONEGA, GA. 
Georgia. "o Finally, Mr. Edwin C. Eckel has recently described the "Gold and pyrite 
deposits of the Dahlonega district," b in "Contributions to economic geology for 1902." 
It will be seen from this list that the district has received a considerable amount of atten- 
tion, and that the main features of the occurrence of the mineral deposits are fairly well 
known. It is not the purpose of the present contribution to present a detailed description, 
nor a complete one, of the Dahlonega mines. Indeed, for such a purpose the time allotted 
was by far too short. It is intended, however, to bring out in a little more detail than has 
been done before a few of the petrographic and mineralogical features, by which, perhaps, 
a somewhat clearer light may be thrown on the true character and origin of that peculiar 
class of deposits to which these gold-quartz veins belong. 
The general geology of the district has been outlined by several of the writers mentioned 
above, especially by Eckel, and to the description of the main relations of the rocks there 
is but little to add. 
The two most common rocks of the district are a mica schist and an amphibolite. The 
mica schist, which is the prevailing rock, is exposed, for instance, at the Preacher Cut, at 
the Benning mine, along Yahoola Creek, and in many other places. The rocks strike in 
general about N. 60° E. and dip at a high angle to the east, but both strike and dip are 
subject to abrupt variations. The mica schists are, in general, dark gray to dark brown 
and medium to fine grained. In places they approach perfect fissility, but ordinarily 
show curved and irregular surfaces of schistosity which are covered with glistening scales 
of biotite and muscovite. One of the most typical rocks is that exposed at the Preacher 
Cut, about one-half mile south of the town of Dahlonega. (See fig. 15.) This is a fine- 
grained brownish-gray schist. The small flakes of biotite have accumulated on the cleavage 
faces, which show fairly good fissility. Under the microscope the rock shows quartz 
mosaic with very few feldspar grains. Embedded in this mosaic lie abundant idioblasts of 
magnetite; brownish-green biotite in parallel orientation; straight, small muscovite foils, 
also mainly extended along one plane; and finally, rather abundant, well-developed, 
small bluish-gray prisms of tourmaline. The structure is typically crystalloblastic, to use 
the term recently introduced by Prof. F. Beeke, of Vienna, c 
The origin of a rock so thoroughly recrystallized as this is always open to some doubt, 
but I consider it reasonably certain that the quart /.-mica schist of the Preacher Cut is of 
sedimentary origin. The consensus of opinion thus far regarding the mica schists appears 
to be that they are not indisputably sedimentary rocks. The normal schist of the country, 
wherever good exposures are available, proves to be similar to this specimen just described, 
although the grain is usually somewhat coarser and the sedimentary origin, though proba- 
ble, is less distinctly indicated. A specimen of dark brownish-gray mica schist, from the 
Jumbo mine, shows again a mosaic of quartz, with a few grains of albite. This mosaic 
contains abundant dirty-brown, sharply outlined foils of biotite and smaller ones of mus- 
covite. Pyrrhotite is present in small anhedrons, but no muscovite was observed. The 
structure here also is typically crystalloblastic. 
No further clew has been found as to the age of the schists. They have, in common 
with all the other rocks of the district, been regarded as pre-Cambrian by Becker and 
other observers, but Eckel is inclined to question this conclusion and thinks that they may 
possibly be of Cambrian or Lower Silurian age. So far as known, however, no Cambrian 
rocks in the South are intruded by granite, but, as is shown on page 122, these mica schists 
contain considerable bodies of such intrusives. 
As emphasized by previous writers, several large and irregular bodies of amphibolite 
occur in the district, as well as in adjoining regions. The contacts beween amphibolite 
and mica schist are usually sharply defined. In some places, as at the Preacher Cut, the 
relation of the two rocks decidedly indicates that the amphibolite is intrusive into the 
a Bull. Georgia Geol. Survey, No. 4-A. 
*>Bull. U. S. Geol. Survey, No. 213, 1903, pp. 57-63. 
c Ueber Mineralbestand und Struktur der kristallinisehen Schiefcr: Sitz.-Ber. d. Wiener Akademie, 
May 7, 1903. 
