ANORTHOSITE-GABBRO IN NORTHERN NEW YORK 30 
country rock are not very sharp. No. 49 of the table gives the 
mineral content of a thin section of the dike rock. Little or no 
granulation isshown. ‘The scapolite, which is very clear and fresh, 
occurs mostly in the form of irregular grains as inclusions in the 
feldspar. Since the scapolite grains are variously oriented in the 
feldspar and their contacts are sharp, it is evident not only that 
the scapolite crystallized before the plagioclase, but also that it is 
not merely a decomposition product of the feldspar. Either the 
scapolite is of primary origin, or it somehow represents recrystal- 
lized material. 
On a little hill at locality 10 several similar dikes were observed. 
Some of these show a moderate degree of foliation. Others occur 
here and there in the anorthosite-gabbro at localities 6, 7, 11, 12, 
and 13. Still others fill many of the cracks in the prominent 
zone of fractured and crushed anorthosite-gabbro described below. 
On the one hand, the true dike character of these white rocks 
and their strike across the foliation of the country rock at high 
angles prove that they were intruded after the anorthosite-gabbro, 
which contains them, had almost or completely solidified. On 
the other hand, their lack of sharp contacts indicates that they 
were intruded while the anorthosite-gabbro was still hot enough 
to allow some merging of the dike materials with the walls. The 
dike material probably originated by differentiation in a still more 
or less liquid portion at a lower level and was then forced into 
fissures in a higher, cooler portion of the anorthosite-gabbro body. 
The dikes are, according to this view, satellitic dikes of the 
anorthosite-gabbro. 
HORNBLENDITE DIKES 
These are remarkable dikes consisting of pure hornblende. 
Altogether in the northern one-third of the area of anorthosite- 
gabbro many dozens of the hornblendite dikes were observed. 
They are generally grouped in certain portions of the anorthosite- 
gabbro where it has been fractured. At locality 10 many cracks, 
commonly in the form of a network in the light-gray, moderately 
coarse-grained, little foliated gabbro, are filled with small dikes 
of moderately coarse-grained pure hornblende. Contacts of the 
