JOHNSON: TALLULAH DISTRICT. 
223 
Rock Types. 
Mica schist .— By far the greater portion of the Tallulah region 
consists of rocks belonging to the mica-schist series. These rocks are 
extremely variable, presenting phases consisting largely of black 
biotite, others in which biotite and muscovite mingle with abundant 
quartz, and still others containing muscovite and quartz alone. In 
texture every gradation from very fine to coarse grained is represented. 
The schistosity may be very marked or scarcely perceptible in the 
hand specimen. Alteration often changes the surface portions of 
these rocks to beds of red and yellow sands. 
With decrease in mica these schists grade toward the fairly pure 
quartzites, described below. Coarse-grained, feldspathic varieties 
give transition members between the more typical mica schists and 
the bands of gneiss. Both the quartzites and the bands of gneiss, 
as well as the slate and limestone belts, occur within the far more 
extensive mica-schist series, and seem to be parallel with the foliation 
of the schists. This foliation is variable, but has a general north¬ 
east-southwest strike, and a southeast dip. 
The mica-schist series has not strongly resisted the actions of 
weathering and erosion, and we now find these rocks covered with 
red soil over a large part of the area, while even the smaller streams 
find it an easy matter to carve out deep valleys in them. 
Quartz gneiss .— Within the mica-schist series, described above, 
are bands of somewhat more resistant rock, containing a large per¬ 
centage of quartz, but with sufficient feldspar or mica (or both) to 
constitute a source of weakness as compared with the true quartzites. 
These rocks are coarser-grained and have a coarser type of foliation 
than the true schists to which they are closely related, and may 
be called quartz gneisses. 
In the process of weathering, the gneisses prove a little more resist¬ 
ant than the schists, and stand out as layers of harder rock in the 
railroad cuts and valley sides. Stream erosion is not seriously re¬ 
tarded by the bands, however, although minor falls on the smaller 
streams are often located on them. The same is true of the more 
resistant phases of the mica schists. 
Quartzite .— This rock is of prime interest to the student of the 
Tallulah district because of its close relation to the most striking 
