278 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
“The mica ranges from silvery white to dark brown in color. It is 
always highly crystallized, and well defined hexagonal crystals two 
inches in diameter are very common.* * * The mineral forms only 
about 5 per cent of the granite, and though sometimes distributed 
generally through the mass, it is more often found in bunches or 
segregations. It was observed that it rarely accompanies the feld- 
spar alone, but is almost always associated with quartz.” 
“Besides the three minerals essential to the formation of granite 
the only ones found in abundance are rose quartz and tourmaline. 
The latter is quite common and sometimes composes 3 or 4 per cent 
of the granite. Itis usually but not exclusively associated with quartz. 
It is black in color, and is generally highly crystallized, though some- 
times massive.” 
The granite dikes of the Nigger Hill region fifteen miles to the west 
of Whitewood Peak, while in general finer grained and nearer typical 
granites, have occasional pegmatitic facies which resemble the granite 
here described, and are probably the nearest outcrops of a similar 
rock. (Darton b, p. 4.) 
The occurrence of the granite and schist in this place may be ex- 
plained in three ways. ‘The Algonkian may be in place under the 
Cambrian, and revealed by the fault, or it may be a small wedge 
broken off from the wall of the conduit of the laccolith and carried up 
with the Cambrian above, or it may be an inclusion from a great 
depth, brought up by the porphyry, which spread out between the 
Algonkian and the Cambrian, and thus the schist fragment became 
wedged or frozen against the bottom of the Cambrian. 
The first of these explanations is hardly tenable, for the fault, 
though of considerable throw in the middle, fades out away from the 
porphyry intrusion, and hence seems to be dependent directly upon 
the laccolith. Also, to all appearance the Algonkian rests upon the 
porphyry and hence cannot be of much greater depth than is exposed 
in the section. 
The supposition that the Algonkian is part of the underlying floor 
on which the Cambrian rested, brought up with the doming of the 
Palaeozoic sediments by the intrusion of the porphyry, has several 
points in its favor. (See Section, Plate 1). It is possible that, given 
a conduit with sloping walls, such as would be necessary for the pro- 
duction of an unsymmetrical laccolith, a part of the hanging wall of 
the conduit would be broken off and forced, by the pressure of the 
porphyry beneath, to cling to the base of the Cambrian above it. 
Although the actual contact of the Cambrian and Algonkian was not 
