350 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



developed pinacoidal and prismatic cleavages, often twinned three and four 

 fold after the usual law. 



At the eastern foot of "The Rocks," in Hatfield, 400 feet west of D. 

 Glasner's, there occurs a limited amount of a peculiar contact product of the 

 tonalite. It is a compact, quartzlike, massive rock, red, mottled with g-reen. 

 The reddish parts are a granular quartz mass, full of small red garnets; the 

 green parts are patches of a pale-green hornblende, with grains of magnetite, 

 and crystallizing so as to include many grains of the other constituents. 



Under the microscope the quartz is full of sheets of granitic fluid 

 cavities, rarely with moAaug bubbles, and is without microlites. Feldspar 

 is represented by opaque white grains, changed wholly into a j^arallel 

 fibrous mass of scales of muscovite. Grarnet is in bright yellowish-red clus- 

 tered grains. The hornblende often contains remnants of a pale-green, non- 

 dichroic pyroxene, extinction 37°, and showing basal cleavage. Beautiful 

 tourmaline crystals appear, which are strongly dichroic, violet to black, 

 several transparent and colorless, but with black heads, the rest colorless. 



The fibrous hornblende runs through the mass in parallel elongate 

 rods, so as to strongly recall a scolithus quartzite in which tlie tubes had 

 been filled with actinolite. This is now mostly changed to a mixture of 

 serpentine and calcite, which effervesces strongly with acid and leaves 

 behind a fibrous white mass resembhng tremolite, which seems to be fibrous 

 quartz. 



An entirely similar rock occurs in Amherst at the north end of Pros- 

 pect street, on the hillside east of North Amherst, and just north of South 

 Amherst. At the first-named locality it is filled with bright spangles of 

 graphite, and in all the other places it is associated with the highly meta- 

 morphosed and granite-soaked schists and appears to be a metamorjjhic 

 rock, and in the Hatfield occurrence it may also be a result of contact 

 metamorphism. I hoped for a long time to be able to prove it to contain 

 scolithus. 



It seems to have been formed as a contact product of one of the beds 

 of limestone that occur in the Conway schists. 



