26 GEOLOGY OP OLD HAMPSHIRE COUNTY, MASS. 



An analysis performecl in the laboratory of Amherst College by Mr. 

 F. H. Fitts gave the following results: 



Analynis of Hinsdale limestone. 



The chondrodite is disseminated through the rock in yellow patches 

 elongate and parallel to one another, and as it in places changes into black 

 patches by the admixture with it of a green mica and magnetite the resem- 

 blance to the boltonite from Bolton, Massachusetts, is striking, especially in 

 specimens of the latter which are changing to serpentine. In large masses 

 it is a rich deep-red, like the chondrodite from the Tilly Foster mine. Under 

 the microscope the patches of the mineral are seen to be made up of crys- 

 alline grains fresh and free from inclusions, and enwrapped by scales of at 

 pale-green micaceous mineral, without any indication that the one mineral 

 has been derived from the other. Tlie mineral shows strong dichroism, 

 honey-yellow to deep red-brown. Toward the surface of the ledge the 

 chonch'odite weathers to a honey-yellow opaque mass. 



The phlogopite is in small, thick crystals with rounded borders, having 

 exactly the same bronzy color as the phlog02iite from Templeton, Canada. 

 Its crystals are generally surrounded by a band of scales of greenish-gray 

 biotite. Both minerals are fresh, and there is no indication of a transition 

 of one to the other. The mineral is optically negative and has the same 

 axial angle as the Templeton |)hlogopite. 



The biotite is disseminated in black scales through some parts of the 

 rocks; at times as isolated crystals with rounded contours; at times bordering 

 the phlogopite in greenish-gray, matted scales, or the chondrodite in thinner, 

 deeper-green scales. All these occvn-rences are nearly uniaxial and negative. 



The pyroxene occurs in dark-green grains of coccolite scattered through 

 the limestone and in small, stout, limpid emerald-green prisms in the pink 

 variety of tlie rock. 



The magnetite and pyrite are in small crystals and crystalline grains, 



