QUARRY MATERIALS OF NEW YORK 97 



horizontal. It possesses a marked rift and grain structure which 

 follows the direction of the vertical joint systems and which has 

 already been described in the earlier discussion of that structure. 

 Blocks of any merchantable size can be quarried : one containing 

 about 6000 cubic feet was exposed in the course of operations in 

 1911. 



The same character of rock extends eastward from this opening 

 on to the Loren Williams place, between the North Jay and Stickney 

 Bridge roads, where there is a very extensive exposure and the 

 outcrop is found on the sides and top of the knob next south of 

 the quarry opening, but the rock here has a coarser texture with a 

 larger proportion of uncrushed feldspar. 



Microscopic examination. Thin sections of the anorthosite ex- 

 amined under the microscope reveal its simple mineral character. 

 It is mainly feldspar of one kind, a basic plagioclase corresponding 

 to labradorite in optical properties. The individuals have been 

 broken down to small grains 2 or 3 mm in diameter, which are 

 interlocked, however, as thoroughly as the components of any 

 granite. Effects of compression are also evidenced by strain 

 shadows in the larger residual crystals. The feldspar shows some 

 alteration to mica around the borders, but otherwise is fresh. The 

 dark constituents are hornblende and pyroxene, frequently inter- 

 grown and showing irregular boundaries. There is a little magnetite 

 or ilmenite in fine particles, but no pyrite. 



Physical tests. The results of physical tests indicate that the 

 anorthosite meets all practical requirements for a building stone. 

 The crushing strength measured on a tube tooled down but not 

 polished was 14,735 pounds a square inch, or equal to that of an 

 average granite. The specific gravity is 2.75, or a little heavier than 

 granite, corresponding to a weight of 172 pounds to the cubic foot. 

 The absorption is low, with a ratio of .127 per cent. The hardness, 

 according to the tests of the bureau of research, State Department 

 of Highways, is 17.6 and the toughness 6. Another sample of 

 anorthosite from Ausable Forks, locality unspecified, showed the 

 following results: specific gravity 2.74; abrasion (French coeffi- 

 cient) 10.5; hardness 18.7; toughness 10. 



Red granite, Ausable Forks 



An outcrop of granite on the Clintonville road 2 miles east of 

 Ausable Forks has afforded a limited quantity of monumental 

 stone of which some has been used locally and the rest shipped to 



