38 WILLIAM J. MILLER 
magnetite and a little pyrite. No. 52 of the table shows the simple 
but rather remarkable mineral content of a thin section of one of 
these dikes. The scapolite is clear and fresh in the form of irregular 
grains. The hornblende is the common variety with pleochroism 
ranging from dark green to greenish yellow. Nearly all the min- 
erals are distinctly elongated parallel to the foliation. There 
seems to be no granulation. These dikes have more or less indefi- 
nite boundaries against the normal gabbro into which they fray 
out most irregularly. They seldom exceed a foot in width. The 
highly foliated structure of dikes arranged like these in normal 
gabbro cannot have resulted from pressure brought to bear upon 
the whole mass of rock after it had all become consolidated. It is 
evident that we are here dealing with a remarkable case of primary 
foliation developed to a high degree in small dikes before their 
final consolidation. The lack of sharp contacts points to the 
intrusion of the dike material into the gabbro while the latter was 
still hot, though nearly or quite consolidated. 
In the light-gray anorthosite-gabbro of the northern portion 
of the area, some dark, hornblende-rich, well-foliated dikelike 
bands occur. In some cases the contacts are fairly sharp, and in 
others they are not. Most of these bands quite certainly represent 
intrusions into the still hot but nearly or quite solidified country 
rock, and their foliation is of primary origin. None of these bands 
show a network arrangement. Whether or not they, too, are rich 
in scapolite is not known. 
WHITE DIKES RICH IN PLAGIOCLASE AND SCAPOLITE 
At a number of localities white dikes were observed to cut the 
anorthosite-gabbro and gabbro. A good display of such dikes 
may be seen in a ledge at locality 5 (see Fig. 3). The main rock 
of the ledge is gray, medium-grained, well-foliated gabbro varying 
to anorthosite-gabbro. Several white dikes ranging in width from 
one to several inches cut across the foliation of the gabbro at high 
angles. These dikes, which are roughly parallel and traceable 
for a rod or more, contain a maximum of not more than a few per 
cent of dark minerals. They are fine grained with some scattering 
feldspars up to one-half an inch in length. Contacts against the 
