132 PROCEEDINGS OF THE AMERICAN ACADEMY. 



14, Plate 2, is a microphotograph of some of these zircon-quartz 

 groups. 



Mr. Dale * states that these spots consist of magnetite, titanite, 

 epidote, zircon, allanite, fluorite, aegirite and quartz. So far as the 

 present investigation has shown the iron oxide is practically all 

 ilmenite, nor has titanite or epidote been identified in the material 

 at our disposal. Two or three minute, dark reddish grains with a 

 highly resinous lustre have been noted macroscopically, and are not 

 improbably allanite, though this has not been positively ascertained on 

 account of the very meagre amount. Ilmenite and hematite besides 

 the mode of occurrence noted, occur frequently in the form of tabular 

 crystals lying along the sides, or between the cleavages of the feldspars 

 and in the aegirite. The parisite has been observed to occur in crystals, 

 a millimeter in diameter closely associated with aegirite crystals, quartz 

 and fluorite, and clearly belongs, as in the other pegmatites, to the last 

 stage of crystallization of the pipes, and is apparently pneumatolitic in 

 origin. It may be noted that small amounts of galena, sphalerite, 

 chalcopyrite, molybdenite occur in small grains here and there through 

 the pegmatite. For other details relating to the minerals see the later 

 description of the large pipe of the Fallon quarry and the special 

 descriptions beyond. 



The Fallon Quarry Pegmatites. 



The first pegmatite discovered in the Fallon quarry outcropped at 

 the surface on the south rim of the quarry, where a small remnant of 

 it still remains. From this point the pegmatite, having a similar pipe- 

 like form, and quite similar otherwise to the pegmatite in the Ballou 

 quarry, dipped down into the granite to the north at an angle of about 

 45°. Following this course, it extended to a depth of about 75 feet 

 (vert.) and then terminated. There is now no trace of it in the bottom 

 of the quarry, but many fragments of it, still remaining on the dump, 

 show clearly its structure and composition. 



The second and far more interesting pegmatite follows the same 

 general direction but appears to have flatter dip, and lies below and to 

 the south of the first. The uppermost part yet exposed appears in 

 the southern wall of the quarry about fifty feet below the surface. 

 Here it resembles the first pipe except that it is larger. Along its 

 downward extension, it increases in size, becomes rudely elliptical in 

 cross-section, the major axis being vertical, and contains centrally 

 toward its lower end a remarkable pocket. A few feet below the 

 pocket the pegmatite terminates rather abruptly. Its total length as 



* Bull. U. S. Geol. Sur., No. 354, p. 50. 



