32 GEOLOfiY 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 coruiection with a trap dyke. On being cut and polished, 

 it was foiuid 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 hkc the ordinary trap of this region. 

 One locality is known on this river, wiiich it crosses one or one and a iialf 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 pvu-sues 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 coimty, 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. Tliey 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 doubtfid whether this property exists at all, though 

 it exhibits a slight change of lustre and color when placed in difiercnt positions as it regards 

 the Ught. 



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 substance : it is probably analogous to the porcelain clays. 



Limits of the Hypersthene 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 tlie 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 Chamiihuii, would be very nearly on the northwestern range. 

 The rock may be traced on the lake sliore 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. 



