136 



GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



Starting at the north end of the great amphiboUte bed and at or near 

 its junction with the sericite-schist on the east — that is, I suppose, its former 

 upper sm-face — the first exposure of the emery, and the most interesting one 

 offered for study at present, occurs in a ledge pi'ojecting- into the Agawam 

 River on its left bank near the most northerly railroad bridge over the river 

 in Chester, north of L. Otis's house. 



Fig. 6 represents this reef, which projects into the river, where the 

 wear of liigh water keeps a fresh surface suitable for study. 



The country rock is an epidotic 

 amphibolite (a), contorted and thin- 

 laminated. The tortuous lines in the 

 drawing represent the foliation, and 

 along the western side of the principal 

 vein, so far as it retains its greater 

 thickness, the laminae bend around, often 

 quite sharply, so as to end abruptly 

 against the emery vein, the lamination 

 being at times continued thi'ough the 

 "fringe rock" (c). On the west of 

 the narrowed portion of the vein, as 

 well as along the whole eastern side 

 of the same, the lamination of the 

 schist acconunodates itself quite accu- 

 ratel}^ to the irregular boundary of 

 the vein. 



Around the smaller vein to the 

 east the structure of the schist is still 

 more complex, and in part, especially in the small mass which is wholly 

 inclosed in the vein, the lamination is entirely obliterated, and filaments 

 from the vein are spun out into the schist until they become as thin as a 

 knife blade. 



A heavy vein of white quartz (d) runs parallel to the jnain vein in its 

 contracted portion, at a distance from it of 1 to 2 feet, and bunches out 

 several times to a width of a foot or more. 



The emery vein (&) where it comes out from the bank is scarcely a 

 foot wide and is growing thinner. It expands northerly, at first quite 



Fig. 6. — Map of emery veins in epidote-amphibolite at 

 north end of bed on the hank of the Westfield Kiver, Ches- 

 ter, a, Epidote-amphibolite: &, magnetite-emery beds; 

 c, biotite fringe rock ; d, quartz veins ; e. tourmaline. 



