GENERAL GEOLOGY. 
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mica schist and that it was originally a diorite or a diabase which has been deeply altered 
by dynamometamorphic processes. The strike and dip of the schistosity is, in general, 
conformable to that of the mica schists, but this again is subject to some marked excep- 
tions. The strike and dip of the schistosity vary considerably from place to place. 
The amphibolite is well exposed in the town of Dahlonega, near the Preacher Cut, and 
on the road from Dahlonega to the Lockhart. The amphibolite from the dump of the Crown 
Mountain mine, at the mill below the Preacher Cut, is a typical, dark-green, roughly 
schistose rock of medium grain, in which, by the naked eye, may be distinguished small 
prisms of amphibole with specks of pyrrhotite. In places narrow streaks appear in which 
Shaded areas represent open cuts 
Fig. 15. — Sketch map of the vicinity of Dahlonega, Ga., showing location of mines. 
the feldspar prevails over the amphibole, thus giving a lighter, greenish-white aspect to the 
rock. The constituents, as seen under the microscope, comprise green amphibole, chlorite, 
calcite, quartz, albite (?), magnetite or ilmenite, pyrrhotite, and chalcopyrite. The struc- 
ture of the rock is characteristically crystalloblastic. Thorough recrystallization has 
taken place, and the principal mass now consists of a quartz-feldspar mosaic in which lie 
embedded ragged and elongated grains of hornblende, some of them inclosing small parts 
of the mosaic. The mosaic contains very few striated feldspar grains, but much feldspar 
is present, and most of it, as indicated by its optical properties, is an oligoclase, although 
some of it may also be albite. The chlorite has the normal characteristics of that mineral, 
and its occurrence renders it probable that it is wholly derived from the hornblende by 
