198 



GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



remnants of mica-schist which occm* as iuclusions in the great granite 

 mass, and at one point appears a grayish-white, massive, fine-grained rock 

 which proves under the microscope to be a hxbradorite-pyroxene-calcite 

 rock. Treated with acid, it leaves a glassy, friable mass, in which scales of 

 graphite and needles of bright-green actinolite are "sasible. 



Under the microscope it shows an abundance of calcite, multiple 

 twinned; labradorite, extinction 14°, often doubly twinned; and large color- 



Fia. 12. — Surface of black limestone with contorted quartz veins. "Wbately. Scale, ^, 



less pieces of pyroxene, extinction 41°, inclosing many grains of the other 

 constituents. Rounded grains of titanite occur. This may be referred to 

 the graphitic limestone of the Conway mica-schist altered by the granite, and 

 this, in connection with the long distance across the granite area that one 

 can follow the hornblende-schist (see p 190), leads one to conclude that the 

 mica-schist fragments in the granitic area in Williamsburg are also remnants 

 of the Conway schist, and that the "argentine" occurrence in the midst of 



