280 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



This interpretation reduced the number of the hornljlendic bands in 

 the schists to 4 or 5, in place of 8 or 9, and this makes the structure of the 

 whole region much more intelligible. 



On the section line the quartzite band is followed b}- a heavy bed (100 

 feet) of a dark-gray mica-schist (/), much coarser than the beds below and 

 carrying abundantly transversely placed biotite, small garnets, and large 

 staurolite crystals, the latter in single crystals and in twins according to 

 both the common laws. This greater coarseness of the texture and the 

 great abundance of staurolite in the upper beds of the mica-schist are the 

 rule through the whole length of the range, and militate against any attempt 

 to make out repetitions in the series now gone over. This band contains 

 one bed, and is capped by another heavy bed, of massive amphibolite (m), 

 65 to 80 feet thick, which rises in a prominent ridge overlooking an isolated 

 house (W. Sondin's), and is followed by one more repetition of mica-schist 

 (h) and by a great bed and one or more smaller beds of schistose amphibo- 

 lite (o) before a fault is reached. Beyond this a broad area of feldspathic 

 quartzite (^^) — to be described later — continues to the railroad at the 

 northwest corner of Gill. If the section is extended across Grass Hill 

 to the Connecticut River it cuts first a broad continuation of this upper 

 quartzite, followed by a complete repetition of the mica-schist series 

 with five hornljlendie bands, one feldspathic, the eastern sloping down the 

 hillside from the Mount Hermon School buildings to the river, and thus 

 covering a large area. 



Sections can-ied across the area anywhere from the quartzite base south- 

 eastward give substantially the same succession as that detailed above, 

 only for a distance east of this line there is a longitudinal fault and a repe- 

 tition of the beds; so that, starting from the same point as the one chosen 

 for the beginning of that line and going directly east to the sawmill on the 

 South Vernon road, one passes nine distinct hornblende bands, and in almost 

 every case each band is found capped by the whitish schist described above. 

 Also along the State line and for a distance north and south, either by the 

 thinning of the beds of mica-schist or by the slipping of the hornblendic 

 bands over them, the latter are usually approximated, the three bands l^elow 

 the middle band of the quartzite coming into close proximity to one another 

 and to the basal quartzite. The latter is separated by a broad mica-schist 

 valley from a prominent hornblende-rock ridge just in the east edge of the 



