1908\ 
Monazite and Monazite Mining 
69 
Rocks and Soils 
The rocks of the southern Appalachain region have undergone 
extensive weathering and in many places in the Piedmont Plateau, 
especially, are concealed by a thick mantle of residual soil. In 
many sections good outcrops are scarce and are found mostly on 
steep hillsides, along water courses and in road cuts. The resi« 
dual soils often furnish evidence of the nature of underlying rocks 
and can be used as a guide to their determination. It is first 
necessary to learn the different stages of soil formation by the 
examination of many outcrops and their graduations into residual 
soil. 
The Carolina gneiss, on partial disintegration and decomposition, 
commonly forms a gravelly soil with a red clayey matrix. This is 
especially characteristic of the garnetiferous and graphite-cyanite 
types, which are abundant in parts of the monazite region. The 
pebbles are composed of small fragments of the original rock, such 
as tufts of cyanite impregnated »with hematite or limonite, iron 
; stained garnets, or pieces of hematite. On more complete decom- 
position a fine reddish clayey soil results, with no decided character- 
istics. Other types of the Carolina gneiss, in which mica is an 
important constituent, leaves a micaceous soil, much of which 
assumes a purplish color. Granite and its various phases, on 
partial disintegration and decomposition, yields light sandy soils. 
On more complete decomposition the granites yield soils of a light 
to dark reddish color, depending on the quantity of ferromagne- 
sian minerals, as biotite or hornblende, in the original rock. 
The quartz grains of the granite remain as sand mixed through a 
clayey matrix. This quartz sand is almost everywhere to be seen 
i at the immediate surface, from which the clays have been washed 
by rains. Where Carolina gneiss and granite are intimately 
associated . or where pegmatization has been extensive in a body of 
Carolina gneiss, there results a sandy soil, characteristic of granite, 
through which are scattered pebbles of hematite and ferruginous 
cyanite, characteristic of the Carolina gneiss. The relative impor- 
tance of pebbles in such soils decreases as the quantity of pegma- 
i tite or of granite in the rock formations increases. These features 
of the soils are especially marked on the broad, flat ridges charac- 
