T. S. Hunt on Norite Rock. 183 
which abound in the St. Lawrence valley, consist of pure or 
nearly pure feldspar rocks, in which the proportion of foreign - 
minerals will not exceed five hundredths. Hence we have come 
to designate them by the name of labradorite rock. The colors 
of this rock are very generally some shade of blue, from bluish- 
black or violet to bluish-gray, smoky gray or lavender, more 
rarely purplish passing into Aesh red, greenish-blue, and occa- 
i ee bluish-white. The weathered surfaces of 
se labradorite rocks are opaque white. e anorthosites 
which occupy a considerable area in the Adirondack region, as 
described by Emmons in his report on the Geology of the 
Northern district of New York, and as seen by me in hand 
mens, closely resemble the rocks of the Labrador series in 
anada. 
stones and as erupted masses, a so far tes 
it the peculiar character jus 
id 
type of rock 
seems in North America to characterize the Labrador series. 
t may here be remarked as an interesting fact ing on 
the distribution of the Labrador series, that two large boulders. 
of labradorite rock, one of the beautiful dark blue variety, are 
found on Marblehead Neck on the coast of Massachusetts. It 
oe 
