GRANITIC AND ASSOCIATED ROCKS. 631 
slate was, however, met with in the granite ridge fifteen miles south 
of the Boundary Range. ‘The granite at this place is almost purely 
a mixture of feldspar and quartz. No true gneiss was seen in the 
Shasty Mountains. 
Not less common than either of the above varieties is a granite con- 
taining small grains or crystals of hornblende in addition to the mica. 
The hornblende is in some cases very sparsely disseminated, and 
there is an imperceptible gradation from this kind to a fine-grained 
syenite, in which the mica is wholly replaced by hornblende. Both 
feldspathic and albitic granites show these transitions. ‘This syenitic 
rock contains the hornblende in large shining crystals, an inch or two 
long, near the entrance to the Shasty Mountains, about twenty miles 
northwest of the peak. The light and dark green crystals, contrast- 
ing with the white albite, make a handsome rock. Many of the 
syenitic rocks contain little or no quartz. 
In the Shasty Mountains we met with a fine-grained, nearly compact, 
porphyritic rock, of a grayish colour, formed of an intimate mixture 
of albite and quartz speckled with points of hornblende, and spotted 
white with crystals of albite a fourth of an inch long. This grayish 
rock, hardly granular in texture, has little resemblance to the other 
syenites or granites, though intimately associated with an albitic 
granite. 
A rock consisting wholly of greenish-black crystals of hornblende 
was occasionally met with in the Shasty Mountains; and also a 
variety containing acicular crystals of white hornblende or tremolite. 
There are other compact hornblendic rocks, black and uncrystalline, 
which are but a step removed from the syenites, although very unlike 
in appearance; for we find the transition through a variety in which 
the hornblende is partially crystallized. The rock is tough, and looks 
somewhat like certain compact basalts, but is much harder and breaks 
with sharper edges. It gives extremely rough features to the land- 
scape. ‘This rock occurs upon the Shasty River, near where the 
party diverged from it to go southward. It is much fissured 
or cracked, without any appearance of regularity of structure; and 
owing to this peculiarity, the action of the weather or of water, instead 
of smoothing down the points and crests, only makes them more rug- 
ged. A slaty structure is only imperfectly developed in a few iso- 
lated spots of small extent. 
The syenites and compact hornblendic rocks also pass into a compact 
hypersthene rock, which is abundant along Destruction River, (the head 
