514 STRATIGRAPHICAL GEOLOGY. 



porphyritic rock enclosing what appear to be rounded fragments of the 

 dark gneiss, some of which are a foot in diameter. But whatever may 

 ultimately prove to be the true character of these rocks, this section, from 

 the variety of the rocks and their relation one to the other, will always 

 be of interest. 



Granitic Vein-Stones. Although there are many granitic veins in the 

 east part of the Merrimack River Topographical District, yet there is one 

 that can be called preeminently the granitic vein. It is nearly coexten- 

 sive with the fibrolite schist, and follows mainly the axis of a great fold in 

 the strata. It is important, as it contains the workable mica quarries of 

 the state, and many interesting minerals. It is developed to a greater or 

 less extent from Warren to Lempster. It first becomes noticeable on the 

 crest of the ridge of Mt. Carr, where it contains rose-colored quartz. It 

 probably follows this ridge southward, as it is found in Wentworth where 

 the section crosses it. 



North of West Rumney and east of J. Sawyer's, there is a vein that 

 contains beryls, some of which are four inches in diameter. They occur 

 chiefly in the feldspar, are of a yellowish color, and are not very brilliant. 

 There are large boulders with granitic veins on the north-east side of 

 Rattlesnake mountain, and these contain beryl. On the hill south of 

 West Rumney we find the vein, and it continues southward in Groton. 

 Near S. D. Southwick's some brilliant beryls have been found ; some of 

 the larger specimens are six inches in diameter. In the midst of the 

 granitic vein at Southwick's there is a bed of arsenopyrite about a foot 

 across. South, at H. N. Hall's, west of the house, the vein is composed 

 largely of quartz ; and some of the beryls found have their lateral axes 

 two and a half inches in length. Following this vein southward we find 

 large crystals of mica, some of the plates being fifteen or eighteen 

 inches across. East of A. J. McClure's there is a granitic vein in 

 granitic gneiss. From this vein some brilliant beryls and good crystals 

 of mica have been obtained. A vein in the south-west part of the town, 

 which is probably a continuation of the one at Hall's, contains plumose 

 mica. 



East, in Hebron, on the ridge running south from Crosby mountain, 

 there is an extensive vein that carries beryl. Large crystals have been 

 found, but they are generally of a dull greenish color. By patient search 



