eokel] GOLD AND PYRITE OF DAHLONEGA DISTRICT, GA. 59 
seems to be strongly indicated, but farther detailed study will be 
necessary to determine this point. 
Diorite. — Several large bodies of hornblende-schist occur in the area 
under consideration, as well as in adjoining regions to the west and 
south. In general, this rock is a fine-grained, highly sheared horn- 
blende-schist, its schistosity being conformable to that of the mica- 
schists by which it is inclosed. At several points a less metamorphosed 
phase of this hornblende-schist is shown, and it seems certain that it 
was derived from an intrusive diorite. In fresh specimens the diorite 
| is a hard, tine-grained, greenish-black rock, occasionally spotted with 
white feldspar. It weathers to a reddish yellow, and is locally termed 
r brickbat," because, on weathering, it separates into rectangular 
blocks, owing to the presence of three systems of joints. The diorite 
appears to decay more readily than the mica-schists of the region; 
and this ease of decomposition seems to have fixed the location and 
direction of many of the valle3 r s of the area. The hornblende-schist 
is well shown in the court-house square at Dahlonega, and is exposed 
in most of the mines in Findley Ridge. It is an igneous rock, cutting 
the mica-schists; but it was intruded at an early period, and has been 
made thoroughly schistose. In age it is therefore intermediate between 
the mica-schists and the granite next to be described. 
Granite. — A light-colored, coarse-grained granite is exposed at the 
Mary Henry and Bennings mines, and also at several points west of 
Dahlonega. It consists largely of quartz and white feldspar, with 
some biotite. Near the Hand mine it is shown cutting across the 
lamination of the hornblende-schist. It is evidently a comparatively 
late igneous intrusive, having suffered little from shearing or faulting, 
and it may be roughly correlated, in point of age, with the Villa Rica 
granite described by Dr. C. W. Hayes as occurring in the Cartersville 
and Marietta quadrangles. 
THE GOLD ORES AND ORE DEPOSITS. 
As is well known, the earliest gold mining done in the district was 
on the placer deposits occurring along the various rivers and creeks. 
Later the attention of miners was called to the fact that in many 
places the decomposed rocks of the region carried gold, and, accord- 
ingly, sluicing these decomposed rocks came into practice. It was 
soon found, on working through the upper decomposed portions of 
these rocks to the fresh hard rocks below, that the free-milling ore 
found in the upper decomposed rock changed to sulphides in depth. 
In handling these sulphides, stamp milling and amalgamation did not 
recover a sufficiently large proportion of the assay values to justify 
exploitation o f the deposits in hard rock. Chlorination of the sulphides 
was then tried, and has succeeded to a limited extent. 
The placer deposits of the district have undergone treatment many 
Itimes, and in consequence few can now be profitably worked by ordi- 
