162 GEOLOGY OF OLD HAMPSniKE COUNTY, MASS. 



They impress themselves strongly on the topography as they beud north- 

 east from Zoar, in Adams Mountain, but preserve their uniform habit to the 

 State line. 



THE SHELBURNE ANTICLINE. 



This anticline is distinguished strongly from the more southern one by 

 the absence of the sericite-schist, the calciferous mica-schist being separated 

 from the gneiss by only a band of hornblendic rock of no great thickness, 

 with merely a suggestion of the Rowe schist below. 



PETROGKAPHICAL DESCRIPTION. 



Mica-schist from near School No. (3, Charlemont. Rather coarse, liglit- 

 gray rock, with shining muscovite scales and distant large garnets. 



Feldspar can be seen rarely with the lens. One piece gave extinction 

 + 15° '60' in the plane of oo P co (010) when measured from the edge M t, 

 and w^as therefore albite. Another gave extinction +2° 30', and was 

 therefore oligoclase (Ab2 Aiii). 



The feldspar is present in small amount. The garnets are crowded 

 with impurities and polarize distinctly. 



Garnctiferous sericite-schist from Chester. Railroad cutting west of sta- 

 tion. A pale greenish-gray rock, with greasy continuous films of hvdrated 

 muscovite between thin layers of rather coarse-granular quartz, full of 

 pale-red garnets. 



Under the microscope the angularly granular quartz abounds in 

 rounded grains of magnetite, and these two minerals fill the garnets, mag- 

 netite being more abundant in the garnet than outside. The muscovite is 

 in twisted films and radiates in broad plates from the garnets. The latter 

 send out abundant amoeboid processes among the quartz grains. 



Beautiful triangular and doubly terminated tourmalines of greenisli- 

 brown color show exquisite absorption — deep crimson at one end, shading 

 to emerald-gi-een at the other, or to the middle, when the green shades into 

 smoke-brown at the other end. They are thus miniature reproductions 

 of beautiful crystals from Paris, Maine. On rotation the colors change 

 places. A few bright-green chlorite scales appear. The order of formation 

 is: magnetite, tourmaline, quartz, garnet, chlorite, muscovite, while the 

 quartz has formed and re-fonned and some of the present grains inclose all 

 the other constituents. 



