1 58 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



constituents until a hornblende-schist is formed, made up of jet-black needles 

 of hornblende and a little quartz and albite, which differs from the heavy 

 bed of amphibolite below in its deeper color, the lack of visible epidote, 

 and its more friable texture. Scattered tlu'ough the series, however, are 

 other beds of hornblende-schist which do not materially differ from the 

 basal bed. 



A light-green pyroxenite, more or less calcareous, forms small beds of 

 a tough, massive rock at various points throughout the whole extent of the 

 formation. This rock was noted by President Hitchcock under the name 

 augitic gneiss. 



At its southern extremity, in Granville and Russell, the beds become, 

 as an exception, somewhat feldspathic, and biotite and cyanite associate 

 themselves with the muscovite. In the railroad cuts east of Russell station 

 occur beds of a I'ather coarse schist in which, on the lamination faces, the 

 bright black biotite is intergrown with the musco\'ite, the latter suiTounding 

 the former, and the basal cleavages being common. 



COMPARISON WITH THE ROWE SCHIST BELOW. 



The two formations agree in the prevalence of mnscovite-schists, and 

 the liA'dration of the mica is a phenomenon common in the older series, 

 notably where the Chester-Becket road crosses the town line and northward 

 across the State, and then a rock exactly like the prevalent one in the 

 higher series results. The feldspathic character of the lower series is not 

 at all projected into the other, and the green tint of the upper beds due to 

 chlorite and to the intercalated bands of hornl^lende and chlorite-schist 

 differentiate the two abundantly. Stratigraphically there is no trace of 

 any break between the two, and as there is, as already described, a well- 

 marked break between the Hoosac feldspathic mica-schist and the Becket 

 gneiss below, and a probable one at the top of the Savoy schist, the 

 Hoosac, Rowe, and Savoy schists are more nearly allied to one another 

 than is any one of these to the adjoining series above and below. 



DETAILED DESCRIPTION AND SECTIONS. 



The facies of the formation changes greatly from north to south. At 

 its southern extremity the two arms which j^ass through Granville are 

 made up of a coarse two-mica, slightly feldspathic schist, rusty, and 

 over large areas barren of accessory minerals, and much cut up in many 



