46 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



extension is shitted more than a mile eastward to the waterworks dam by 

 a fault, and it continues from this point southwardly, passing- east of the 

 "asbestos mine." 



The other great area occupies the eastern portion of Leverett, is cut off 

 on the north by a fault at the Rattlesnake Gutter, and projects southwardly 

 across Shutesbury into the western portion of Pelham, where it ends under 

 Mount Hygeia, approaching near the other band. 



rKTKOGRAPHICAL DESCRIPTION. 



1. Actinolite-fremolife-gneiss from Northfield, east of R. H. Minot's, and 

 adjoining the great north-south fault. A greenish-gray, stretched, ligniform 

 rock, the abundant needles just visible to the eye. In a fresh, granular 

 quartz-orthoclase base the abundant parallel needles of ^Jale-g-reen actino- 

 lite and tremolite appear. They show a delicate, close prismatic cleavage, 

 distant, strong basal parting, and strong absorption and pleochroism. Grreen 

 and brown biotite are abundant, and there is much magnetite. 



This is the only occui-rence of the rock in the western portion of the 

 Pelham area, and it is soon cut off on one side by the fault and on the 

 other by granite. 



3. Micaceous quartzite from Pratts Comer, southwest Shutesbury. In 

 a white, fine-grained, only subgi'anular quartz mass are scattered small, 

 rounded, red scales of biotite. No feldspar. 



Under the microscope the quartz mass shows only rarely a fissure, and 

 is so homogeneous, colorless, and free from foreign bodies that it is invisible 

 in common light. With crossed nicols it shows a most complex mosaic of 

 interlaced grains 



The red scales of biotite are all in parallel planes, and inclose zircons 

 which are surrounded by a marked deep-brown jileochroie border. The 

 zircons are also scattered through the quartz in fine crystals. Red-brown, 

 stout rutile prisms occur smTounded by a granular, colorless leucoxene. 



3. Actinolite-qiiartzite from north side of brook and about 100 feet east 

 of the dam of the Amherst waterworks in Pelham. To the eye the rock 

 is like a fine-grained, white sandstone or crisp, friable quaitzite, with scat- 

 tered needles of pale-green to almost colorless actinolite. The lens rarely 

 detects a grain of feldspar. It is whiter and contains less actinolite than 

 the Mount Hygeia rock, but is closely like it. Under the microscope 



