1908] 
Monazite and Monazite Mining 
67 
present in the pegmatitic material but has generally been plenti- 
fully developed in the mass of the gneiss by metamorphism. The 
feldspar of pegmatized gneisses often assumes a porphyritic form 
producing augen gneisses. The gneisses and schists are often 
banded with or cut at all angles by streaks of pegmatitic or grani- 
tic material. The recrystallization of the gneisses and schists, 
with the development of pegmatitic material or the injection of 
such material through the rocks, may be called pegmatization . In 
many places the process has proceeded so far that it is very diffi- 
cult to distinguish pegmatized gneiss from granite gneiss, especially 
from porphyritic and flow-banded granite gneiss. This difficulty 
is partly due to the fact that granite and pegmatite are composed 
of the same minerals and have no sharp division line between the 
size of their grains. 
The peridotites and allied basic rocks are dark-green to greenish 
black in color and contain one or more of the ferromagnesian 
minerals, olivine, pyroxene, and hornblende as chief constituents. 
So far as known these rocks are of Archaean age and are probably 
genetically connected with the Roan gneiss. Though a relatively 
unimportant rock of the monazite region, these basic rocks gener- 
ally outcrop prominently wherever they occur, and many of the 
outcrops are marked by large rounded “nigger-head” bowlders. 
The peridotites and allied rocks are often altered to talcose or 
chloritic soapstone or serpentine. In some cases this alteration is 
only superficial, but in others whole masses have been so meta- 
morphosed. These rocks generally occur in lens-shaped bodies 
parallel, or nearly so, to the schistosity of the inclosing rocks. 
Quartz diorite of undetermined age is one of the less important 
intrusive rocks of the monazite region. It is a hard, fine grained 
rock, composed of granular quartz and feldspar with varying 
quantities of hornblende. Locally, garnet is distributed pro- 
miscuously through it. Quartz diorite occurs in small dikes, 
from a few inches to several feet thick, cutting the formations at 
various angles. Their size is offset by their abundance in some 
sections and resistance to erosion, owing to which they leave much 
debris over their outcrops in the form of hard rounded bowlders. 
Diabase, probably of Triassic age, is the latest intrusive rock 
known in the monazite region. It is a dense, hard rock of dark 
