Report of the State Geologist. 



gay lakes, lie, the former wholly, and the latter mainly, w ithin its borders, and 

 the latter is, furthermore, a tpiite typical Adirondack lake. 



Series I. The gneisses constitute the larger part of the township, the 

 massive ridge of Dannemora mountain occupying the eastern portion, Mount 

 Lyon in the centre, and the range of hills which extends into Ellenburgh as 

 Kllenburgh mountain <>n the west. Much <>f the gneiss is of the ordinary 

 acid, microperthitic variety, w ith the ever present hands of basic hornblende 

 gneiss On Dannemora mountain, along with the red gneiss, is a w hite gneiss 

 streaked with black, which contains a quite pleochroic green monoelinic 

 pyroxene and much titanite. At Lyon mountain village, the ore-bearing 



gneisses are also pyroxenic. They are well foliated, red gneisses, made up of 

 quartz, orthoclase, plagioclase, green pyroxene, deep orange titanite, a little 

 hornblende and magnetite. The pyroxene is strongly pleochroic, like that at 

 Dannemora, a being greenish-yellow, b and c green. The presence of so much 

 titanite in the rocks enclosing the magnetite deposits is interesting. It never 

 appears as rims round the magnetite, as it does in some of the hornblende 

 gneisses. 



Seines II. Not present in the tow nship so far as know n 

 Series III. A single small knoll of basic gabbro occurs nearly a mile 

 east of the low er end of Chazy lake, w ith gneiss in close proximity on the 

 west, and Potsdam <»n the east, while the gneiss of Dannemora mountain is 

 only two miles away eastward, so that this gabbro is undoubtedly to be 

 classed w ith the smaller masses which occur interbanded with the gneisses. 

 The rock is somewhat gneissoid, but readily identifiable in the field as gabbro. 

 It is not completely granulated, but of the ophitic type, showing large 

 individuals of labradorite and nearly colorless monoelinic pyroxene of 



