546 



Report of the State Geologist. 



of one mile and a half where it crosses the river from Chesterfield, and 

 gradually decreases in w idth going north till the last of it runs under cover 

 two miles north of Keeseville. 



The district furnishes the most typical anorthosite to be found in the 

 county. While the rock is mueh granulated, some of it wholly so, there is 

 still much of it that shows partially unbroken crystals of labradorite that 

 reach, on occasion, a very considerable size, being found up to three inches in 

 length. A considerable part of the rock is almost wholly feldspathic, the 

 ferro-magnesian minerals occurring only in very small amount. The less 

 feldspathic portions of the rock are the most completely granulated, and have 

 a prevailing gneissic habit. In these varieties garnet is very abundant, often 



Cin.ei.ss .Anorthosit* Potsdam Pl«Lstoc«ne. 



imparting a reddish tint to the rock. In them reaction rims are also a feature, 

 and a considerable amount of recrystallization has taken place. Openings 

 have been made in the more feldspathic portions of the rock in the vicinity of 

 Keeseville, and some of it put on the market under the name of "Keeseville 

 granite." It makes a very handsome stone, the large, blue-grey labradorite 

 crystals surrounded by a lighter colored granulated zone giving a very pretty 

 effect : but no tests of its crushing strength have been made, so far as the 

 writer is aware. It seems quite resistant to weathering. 



In several places in this anorthosite area are found bands of basic 

 gabbro. When finely granular, as is commonly the case with the thinner 

 bands, they look like dikes. The larger masses are often less changed and 



