86 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



again well exposed. Northwest of S. A. Bartholomew's house, at his soap- 

 stone quaiTy, some layers of mica-schist are intercalated in the amphibolite. 

 The quaiTv, from which much soapstoue (bed No. 9 ) has been taken for grind- 

 ing, is inclosed in walls of chloritic mica-schist, and lies in the prolongation of 

 a bed of the ordinary amphibolite, which is exposed just north of the opening. 



There is exposed in the north end of the excavation a layer, 1 foot 

 thick, of light-green talc with scattered needles of actinolite, and east of 

 this, one (the same thickness) of a green, soft, scaly chlorite, with here and 

 there larger plates of clinochlore with very divergent optical axes, and 

 magnetite octahedra. Farther south, in the bottom of the quarry, it can 

 be seen that the steatite bed widens rapidly southward to 10 feet, and a mass 

 of light-green fibrous actinolite appears, from which the whole steatite mass 

 seems to have been derived, as it still retains the radiated and matted 

 acicular structure of the actinolite. 



A few rods south of the steatite quarry, and just west of the village of 

 North Blandford, is the great mass of serpentine (bed No. 10) marked 

 upon Walhng's map of the county as "The Crater." The name is said to 

 have originated with Dr. Hitchcock, when he thought the rounded, isolated 

 mass, with a large cavity in its center, proof of the volcanic origin of ser- 

 pentine. It seems to me not improbable that the cavity in question may be 

 an artificial excavation, and it is certain that in early times considerable 

 digging was done there for cliromite. It is an oval mass, 328 feet long and 

 200 feet wide. On the west is a stratum of amphibolite 20 feet thick, which 

 strikes north-south along the side and wraps round the north end until it 

 strikes N. 28° E. This seems to indicate that the change to sei-pentine took 

 place before the final compression of the rock, or that the original rock was 

 different and less comjiressible than the amphibolite. Below is the sericite- 

 schist. The serpentine from this locality is easily distinguished from any 

 other by its compactness, its black-gray color, the abundance of dissemi- 

 nated magnetite, and the nickel-green crust from weathering. 



Along the strike of the rocks southeast by south the ground is much 

 covered and no further outcrops have been found, though the region has 

 been thoroughly searched in prospecting for emery, until the Osborn soap- 

 stone quarry is reached; but several bowlders reported to me by Mr. 

 Bartholomew, viz, serpentine west of the north end of Blair's pond, and 

 soapstone northwest of Pebble's brook, and also west of the Blair's pond 

 road, indicate other deposits in the intervening space. 



