200 MINERALOGY AND’ LITHOLOGY. 
been compared to pepper and salt. These little black specks are found, 
on microscopic examination, to be in part biotite and in part hornblende, 
though, as in the last class, these ingredients are variable, both in their 
amount as relates to one another, and to the mass of the rock. At some 
points, as, for example, at Jackson falls, these rocks are characterized by 
their frequent inclusion of fragments of other rocks. This circumstance, 
among others, has caused them to be all considered as eruptive. Though 
this may not be improbable, this circumstance of itself is not sufficient to 
prove the eruptive origin of a granite, for it has been more than once 
pointed out that some granites are partially fragmental in their nature. 
The little grains of hornblende in thin sections often appear quite well 
crystallized. Plagioclase, and little crystals of apatite, are conspicuous. 
A very peculiar granite has been cut by the railroad at Bemis station. 
It is fine in its texture, and light gray in color. In thin sections its 
accessories are found to be white hornblende and muscovite. Besides 
these, sphene, in irregular grains, is abundantly scattered through it. 
Plagioclase, pyrite, and pyrrhotite are also ingredients. This rock is, 
so far as I am acquainted, an isolated occurrence. 
A granitic rock from Portsmouth contains green dichroic hornblende 
and muscovite, but so much plagioclase that it brings to mind the quartz 
diorites that are found in the region. 
Hlornblende Granites. The granites in which hornblende alone ap- 
pears as the characteristic accessory are fewer in number ¢han the 
last. Prominent among these is the Chocorua granite. In thin sec- 
tions, the hornblende of this granite is very dark in color, and strongly 
dichroic. A little scale of mica is occasionally found. As accessory 
constituents, titanic iron, hematite in blood red, translucent grains, fluor 
spar in grains with an attempt at crystallization, and epidote in grains 
with a most delicate feathery fringe, are present. The orthoclase is 
quite pure, but is made up of those irregular laminze which are repre- 
sented in Fig. 1 on Pl. 8, and which are only seen in polarized light. 
They result from the circumstance that in the two interlaminated parts 
of the crystal the axes of elasticity are somewhat different in their ar- 
rangement, and hence the interference colors obtained in any given posi- 
tion between the Nicol prisms are different. This granite has a greenish 
tint, which is imparted to it by epidote. 
