370 The American Geologist. December, 1894 
stone. Localities F and <t are small isolated outcrops of crys- 
talline limestone situated in the midst of the granitoid 
gneisses, which make up the bulk of the mountain. The 
largest area of crystalline limestone occurs east of the north 
end of the mountain, occupying an area two miles in length 
from north to south, and one-half to three-quarters of a mile 
in width. The surface within this area consists of a succes- 
sion of low ridges and valleys with no definite order, forming 
foot-hills lying between the high crystalline mountain mass 
on the southwest and the alluvium of Pequest meadows on the 
east. 
Petrographical characters of the crystalline limestone and 
associated eruptive rocks. The crystalline limestones of War- 
ren county are more or less coarsely crystalline, varying be- 
tween white and red in color, and containing large amounts 
of accessory metamorphic minerals scattered everywhere 
through them — mainly pyroxene, hornblende, quartz, and 
magnetite. 
The limestones at the north end of the mountain are cut 
with great frequency by eruptive rocks. These are of three 
kinds, diabase, pegmatite, and diorite. Dark, fine-grained 
diabase, in vertical dikes up to fifty feet in thickness, cuts 
the limestone at various points. A coarse pegmatite contain- 
ing considerable amounts of hornblende and magnetite occurs 
sometimes in irregular areas in the limestone, and is probably 
of eruptive origin. The most abundant eruptive rocks occur- 
ring in the area form a series of varying mineralogical com- 
position, but as a whole merit the name of diorites. They 
consist general^ of green monoclinic hornblende and plagio- 
clase, and are then true diorites. Monoclinic pyroxene often 
occurs and the rock is then an augite-diorite. In some cases 
the pyroxene occurs in greater abundance than the hornblende, 
when the rock becomes a gabbro. While typical diorites are 
the most common, all gradations occur between the three va- 
rieties mentioned. The rocks, however, lack the typical dio- 
rite structure. All the principal minerals occur in rounded 
or polygonal grains. This structure is explained by the fact 
thttt the rocks occur in comparative^ small masses, and may 
be supposed to have cooled rapidly, giving no opportunity for 
the different minerals to ciystallize out separately in a defi- 
