THE CHESTER AMPHIBOLITE AND SERPENTINES. 149 



crystals of enstatite, of about the same size and pro})ortions, and with, as 

 the result proved, the same tendency to serpentinization. I may say that 

 transverse sections of crystals, from both the massive and the implanted 

 forms, show the prismatic and two pinacoidal cleavages of enstatite, marked 

 with great regularity by bands of black magnetite dust, even when the 

 whole mass is completely chan^d to serpentine. 



(a) The formation of the enstatite in the limestone is not due to 

 dynamic metamorphism. 



A shearing of the central band of limestone, which has promoted the 

 complete destruction of the enstatite and caused the thin foliation, is very 

 manifest. No one can, however, examine a cubical block of the black 

 mottled marble, where the long rods of enstatite run in all directions 

 without crushing, bending, faulting, or fibrous development, and avoid the 

 conclusion that the mass was free from internal movements during and since 

 their formation. The same must be true of the coarse enstatite rock, found 

 elsewhere, made up of long interlaced crystals. They must, then, have 

 been formed since the erection of the beds into their present vertical ])osi- 

 tion and during their penetration by the abundant granite dikes which cut 

 them. 



(h) The development of enstatite in the limestone, and of the cyanite 

 in the schists, coincides geographically with the spread of the great granite 

 batholites. 



The Chester series — amphibolites, serpentines, pyroxenites, enstatite 

 rock, serpentinic and dolomitic limestones, and steatites — can be traced from 

 the Hoosac Tunnel across the State, and in great loops across Granville, to 

 its disappearance south of Munn's brook. The granitic intrusions extend 

 westward across Granville and Blandford, and are wanting in the neighbor- 

 hood of the band farther north. Where they are present the intenser met- 

 amoi-phism of the schists is indicated by their coarser crystallization, the 

 lack of sericite, and the great abundance of cyanite, which of all the purely 

 aluminous silicates indicates the strongest metamorphic agencies. 



The development of enstatite in the limestone is also coincident with 

 the presence of the granite, and represents a stronger metamorphism of the 

 dolomite dependent upon its influence, and the most northerly appearance 

 of the enstatite and coarse pyroxenite is at Osborn's quany in Blandford, 

 just where the western boundary of the granitic area leaves the line of the 



