14(5 



GEEEN MOUNTAINS IN MASSACHUSETTS. 



These facts indicate that stratification foliation and cleavage foliation 

 may he equally or unequally dominant or microscopic. 



Fig. 45. — Microscopic drawing of about £ inch square of a thin section of a specimen of schist from locality 741. on 



East n main, cnlargenu nt 39 diameters. The light portions are mainly quartz, the dark mainly sericite and chlorite. 



I to- central plication shows the development of cleavage from a slight crinkling to a complete fault. Another cleavage 

 plane, abont J of a millimeter to the right, contains some ferruginous matter. 



CASE VI. 



Frequently small lenticular masses or laminae of quartz of irregular 

 thickness occur in the schists. Their form and direction are sometimes so 

 irregular as to give no information as to structure, but thev sometimes show 

 a general parallelism either to the cleavage foliation or to the stratification 

 foliation or to both. Fig. 4(> represents a specimen from locality 550, about 

 1,500 feet south and 500 feet below the Greylock tower. 



The specimen consists of two parts, a mass of schist about 3 indies 

 thick, capped by a quartz lamina about a half-inch thick, which undulates 

 conformably to the general stratification foliation of the schist. The strati- 

 fication foliation dips west at a very low angle, while the cleavage foliation 



