246 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



THE FIBROLITE-SCHIST INCLUSIONS. 



The most instructive occurrence to prove the eruptive character of the 

 touahte and to ilhistrate its contact phenomena is found in the broad sheet 

 of coarse fibroHte-schist which runs two miles southwest from "Slab City," 

 in the east of Belchertown, to end at the house of V. H. Pease. In the mid- 

 dle of the road that runs along its southern border at the western Cloug-h 

 house — this and the Pease house being- the only ones on this road — at a 

 watering trough, a brook crosses the road, coming down over the rocks, and 

 30 feet above the road one sees the contact of the tonalite and the schists 

 above it, and at the trough the quartzite appears as a granular quartz- 

 epidote rock. The bright yellow-green epidote is in rounded crystals, each 

 sm-rounded by a white spot, from which the iron has gone to supply the 

 epidote crystal. 



At the northeast end of the inclusion, at G. Robinson's, a dark biotite 

 schistose gneiss, like that found at Baggs Hill, dips normally under the 

 fibrolite-schist. Tlie biotite Is black, with a shade of green, and makes 

 continuous films through the granular quartz mass. Below this gneiss are 

 beds of a thin-fissile, slightly micaceovis quartzite. 



This fixes the position of the fibrolite-schist as the equivalent of the 

 upper mica-schist, as does the fact that it lies in continuation of the mica- 

 schists in Enfield, and the latter are the only beds sufficiently argillaceous 

 to have fui'nished material for so much aluminous silicate. These same 

 mica-schists grade eastward into fibrolite-schist and continue across 

 Worcester CountA', but they are rarely so coarse as here. 



PETEOGRAPHICAL DESCRIPTION. 



Fihrolitc-chJoritc-schist, from bowlder in cutting on Massachusetts Cen- 

 tral Railroad, South Belchertown, but coming doubtless from the contact 

 zone of the granite; a stretched gneiss-like rock (if gray color, with shade 

 of green and showing much fibrolite. 



Under the microscope radiated fibrous tufts of a green, chloritic mineral 

 inclose much graphite in notched plates, and this chlorite is associated with 

 an abundance of large gai'uet grains free from the same inclusions, and 

 these together frame large grains of quartz full of rutile needles. Tlie 

 quartz polarizes as a mass of grains and is plainly secondary. The fibrolite 

 is abundantly woven through the whole. 



