240 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



brian gneiss. I am thus constrained to leave the Orange band with the 

 gneisses and to assign the Hardwiek band to the granites, in spite of their 

 resemblances. The latter band widens as it goes north, and crosses the State 

 line with the whole width of the country between Royalston and Winchen- 

 don, and ends with the characteristic blunt point north of Fitzwilliam; and 

 the line of the syncline continued passes under Monadnock, and the granites 

 possibly continue along this line, beneath the mountain, and have caused the 

 large development of andalusite in its schists, as they have on the border of 

 the Princeton band and in the center of the Worcester slates. Only its 

 southern, narrowed end enters the territory imder review, in Ware, and runs 

 down the eastern portion of the Palmer quadrangle. Across the whole State 

 the narrower western portion of this Ijand is a very dark granitite — generally 

 dark from excess of black biotite, more rarely by the presence of jet-black 

 hornblende. The eastern portion is an excellent biotite-muscovite-granite, 

 like that of Fitzwilliam. The darker portion is well exposed in the railroad 

 cut at Gilbertville, and is described below. Where the Coys Hill granitite 

 crosses it it carries large "augen" of adularia, like the adjoining schists. It 

 is thus older than the post-Carbonifei'ous granites. 



The rock may be studied Ijest along the road running east from South 

 Monson and near the east line of the town. At L. Bradway's it resembles 

 a good typical Monson gneiss, as also at B. Brook's. At T. SutlefFs a black 

 granular hornblende-gTanite, a dark biotite-granite with amber feldspar, and 

 a granulite full of shining-white fibrolite occur on this teiTane. Such fibro- 

 lite always appears to have been dissolved in granite, being derived from 

 the adjacent tibrolite-schists. 



PETROGRAPHICAL DESCRIPTION. 



At the first cutting on the Central Railroad northeast of Gilbertville 

 station, 1 7 feet east of a pegmatite dike, occurs a rather fine-grained granite, 

 nearly black from the abundance of biotite and magnetite, and of slightly 

 subporphyritic aspect from the presence of disseminated scales of biotite, 

 or groups of scales 3-4°"° across. 



Under the microscope it is a wholly fresh, highly crystalline granitoid 

 rock. On a background of closely interlaced grains of orthoclase and plagio- 

 clase an abundance of biotite, magnetite, and epidote appears. Quartz is 

 wholly or almost wholly wanting, and there is no trace of microcline. The 



