CONTACT AROUND BELCHERTOWN TONALITE. 247 



Filrolite-biofite-schist, from south end of the main belt of schist in the 

 granite. This is a coarse schist, showing an abundance of muscovite and 

 biotite, rusty, and containing large spots of gai-net and coarse fibrolite 

 blades, often 3-5'"°' wide. 



Hie .microscope shows many black scales, part of which are l)k)od-rod 

 specular iron, and part seem to be graphite, as they are grown togethei- in 

 long lines and have rounded outlines. There are many rutile needles in 

 the quartz. 



Gat'nei-stauroUte rock, from large bowlder in the first cutting of the 

 Massachusetts Central Railroad south of Belchertown, and coming doubtless 

 from the Ijund (if fibrolite rock to the north. This rock represents the 

 extreme of metamor[)hism reached by the rocks bordering the granite. It 

 is a highly crystalline rock of medium grain. Large patches of gamet 

 and quartz and much biotite are visible to the eye, and the lens detects 

 much staurolite, graphite, and a few shining surfaces of fibrolite. 



Under the microscope nearly half the surface is occupied by stains >- 

 lite; the garnet patches are seen to be made up of congeries of small 

 grains, and these two separate ({uite widely the (piartz patches, which are 

 crowded with fibrolite and rutile microlites and are thus plainly secondary 

 quartz. All these minerals include plates of graphite scales — single or 

 grown together in long series. 



Ejyklofe rod; from Belchertown. This is an interesting product of 

 the contact metamorphism of the tonalite upon the schist. It occurs at the 

 watering trough near the house of J. Clough, in the southeast jjart of 

 Belchertown. The rock has a mottled look; a Avhite groundmass winds 

 among rounded spots of a dark yellowish-green color, made up of biotite 

 and epidote. The rock grades into biotite-g-neiss. 



The epidote is the most abundant constituent, and with a strong lens 

 one can make out the fresh, shining, model-like crystals, regularly dis- 

 seminated, and semiojiaque centrally. With the microscope they are seen 

 to be filled with grains of quartz, of elongate, irregular shapes, and very 

 large in proportion to their host, which crowd the central portion and 

 radiate outward. It contains, also, chlorite scales. Biotite, regularl}- 

 disseminated and strongly dichroic, molds itself to the epidote, as does the 

 rare quartz. Apatite occurs in regular crystals, forming pleochroic rings 

 in the biotite. 



