Granite at Mounts Adam and Eve. 643 



the ore body of the Trotter mine/ and in pegmatitic masses in the 

 abandoned iron mines on the hill north of the depot. It also occurs 

 with pyroxene in the Mud mine at Ogdensburgh, where granitic or 

 dioritic intrusions are well developed. 



Although allanite or orthite has been analyzed from Monroe, a 

 neighboring township, none from Mt. Adam has yet been reported 

 on. Prof. Dennis, of Cornell, who has given much attention to the 

 difficult chemistry of the rare earths, now has some under way. 

 Minute zircons of excellent crystallization are common in the 

 granite, and titanite in rude masses is frequent. Magnetite not 

 infrequently appears. The pegmatitic masses that contain the 

 allanite yield beautiful microscopic crystals of zircon when crushed 

 and panned out. The granite varies in structure and appearance 

 in the Mt. Adam quarries much more than in those of Mt. Eve, 

 and this variability in large part has rendered the former unsuccess- 

 ful. The pegmatitic imperfections have already been cited; but in 

 addition, the normal, coarsely crystalline and relatively light-colored 

 granite changes abruptly into close-grained and dark streaks up to 

 several feet across, which however possess practically the same 

 minerals as the former, although much more dioritic in appearance. 

 They appear to be due to differences in the original magma, as they 

 are certainly not later intrusions. In the applications as a building 

 stone they were of course fatal. 



At the north end of Mt. Eve the granite is quite gneissic, but the 

 same minerals are shown by the sections. Still here, even more than 

 to the south, evidences of djmamic disturbances appear. Crushed 

 crystals of quartz and feldspar, microperthite, and the like are all 

 abundant. In the granite from Round Hill the hornblende gives 

 way to biotite, and some variations of structure are shown. While 

 all the minerals are v^^ell crystallized, the structure occasionally 

 approximates that of quartz-porphyry. In a knob east of Mt. E ve we 

 found fine graphic granite. It is formed of quartz blades in micro- 

 cline of microperthitic habit. In the smaller knobs the granite is 

 prevailingly gneissic. 



1 J. F. Kemp, The Ore-deposits at Franklin Furnace and Ogdensburgh, N. J., 

 Trans. N. Y. Acad. Sci., Oct. 1893. A. S. Eakle, The Allanite of the Trotter 

 Mine, idem, Nov. 1893, Amer. Jour. Sci., April or May, 1894. 



