32 
GEOLOGY OF THE SECOND DISTRICT. 
it was associated in this place with fine crystals of quartz. A very fine specimen of chalce¬ 
dony was found, a few years since, in connection with a trap dyke. On being cut and polished, 
it was found to be a very superior stone ; it is in the possession of Mr. Henderson, 
The porphyries or breccias, which have been found mostly in loose masses upon the beaches 
of the East river, are undoubtedly all of them in veins like the ordinary trap of this region. 
One locality is known on this river, which it crosses one or one and a half miles below the Great 
falls. It is an extremely tough mass, being composed of chalcedony and feldspar, and a de¬ 
composable green substance. It is about two feet wide, and pursues the general course of the 
dykes of this region. 
In addition to the above variety of rocks and minerals, we often find rolled masses of the 
common flesh-colored feldspar or granite, and sometimes handsome specimens of graphic gra¬ 
nite. A variety of feldspar, too, is not unfrequent in veins in the hypersthene, which resembles 
albite ; and it seems to take the place of this mineral, or to hold the same relation to the hy¬ 
persthene rock, that the common albite does to the coarse granites of New-England. It is in 
laminated and stellated masses, like the albite of Chesterfield ; it is not so distinct, nor so 
handsome. It occurs near Westport in Essex county, on the road between Westport and Port 
Henry. 
Of the varieties of the labradorite not yet noticed, is one of a dark bottle green color, in 
crystals, usually associated with many of the ores of Adirondack. They are sometimes two 
or three inches in length, but I have not yet obtained it with natural faces. It is to be procured 
only in cleavage forms, presenting‘broad and slightly striated surfaces. It is more feebly opa¬ 
lescent than the blue variety ; in fact, it is doubtful whether this property exists at all, though 
It exhibits a slight change of lustre and color when placed in different positions as it regards 
the light. 
At the head of one of the branches of the Ausable, this rock passes into a light green and 
nearly compact feldspar. When wet, it is a pale apple green ; but when dry, it is dull, and 
not remarkable for beauty. It decomposes rapidly ; so much so, that the weathered surface 
is covered by a soft putty like substanceit is probably analogous to the porcelain clays. 
Limits of the Hyp&rsthene Rock. 
In travelling north through Warren and Essex counties, boulders of this rock first appear 
on the road side, and in stone fences, near the village of Warrensburgh. They increase 
on going still farther north, and are particularly abundant in the banks of Schroon river, and 
diluvial gravel beds. A few miles south of the village of Schroon, the rock appears in 
place. This may be considered as its southern limit. If a line were drawn on the map about 
northwest to Newcomb, it would mark its southwestern limits ', another line drawn northeast 
to Trembleau Point on Lake Champlain, wovdd be very nearly on the northwestern range. 
The rock may be traced on the lake shore to Willsborough ; the boundaries will be completed 
by drawing a line so as to pass through Westport about three miles from the lake, thence to 
Paradox lake, and the village of Schroon. 
