46 WILLIAM J. MILLER 
pegmatitic juices of magma, sharp contacts against the country 
rock would not be expected except where the magma had risen 
far enough to have lost its dissolving power. Further light is 
thrown upon the problem of the origin of this pegmatite rich in 
pyroxene in the discussion of the pyroxenite dikes (see below) 
which occur in the adjacent granite. 
PYROXENITE DIKES IN THE ASSOCIATED GRANITE 
Near the very northern end of the area of anorthosite-gabbro 
(locality 4), pyroxene-rich dikes cut a ledge of medium-grained, 
well-foliated, moderately hornblendic, pink granite close to its 
contact with the gabbro. Figure 5 shows the general relationships. 
On the left side curving parallel cracks in the granite are filled 
with dikes of pure to nearly pure, moderately coarse-grained, dark- 
green monoclinic pyroxene (apparently common augite). They 
contain only a few scattering crystals of orthoclase and quartz. 
None of these dikes is over an inch in width, and they all pinch 
out in the granite. Seven of them, up to two yards long, are 
perfectly arranged as a curved series one above the other in the 
face of the ledge. ‘They show sharp contacts, and they cut across 
the foliation of the granite at high angles. On the right side 
(see Fig. 5) there are five or six coarser, crudely parallel, nearly 
vertical dikes, up to several inches each in width, in sharp contact 
with the granite. Crystals range up to two inches across. These 
dikes contain scattering crystals of orthoclase and quartz, but 
never more than to per cent. Between the two sets of dikes just 
described there is an irregular mass of very coarse pegmatite with 
crystals of quartz, orthoclase, and pyroxene up to six inches in 
length, but here the pyroxene is subordinate in amount. ‘This mass 
shows only moderately sharp contacts against the granite. 
It seems most probable that the pyroxene of both the pure 
pyroxene and pyroxene-rich pegmatite dikes was derived from the 
anorthosite-gabbro. Where the magma or juices passed through 
‘the gabbro, the pyroxene is believed to represent dissolved or 
digested and recrystallized ferromagnesian material. 
It is important to bear in mind that the dikes of pure pyroxenite, 
as well as.the dikes of hornblendite above described, are examples 
