VI 



CONTENTS. 



Chapter V. — The Lower Cambrian gneisses — Continued. Pagf- 

 The Monson gneiss — Continued. 



The Polham and Wilbraham area — Continued. 



Saxouite and serpentine in Monson gneiss 47 



The Pelham asbestos quarry 47 



Petrographical description 52 



The Pelham serpentine .55 



The Shutesbur y serpentine .55 



The New Salem serpentine 55 



The Orange and Jlonsou area 56 



General description 57 



Petrographical description .59 



The Monson quarry (lO 



Strength of the Monson gneiss fi3 



Conglomerate structure of the Monson gneiss and sudden expansion of the rock 



in quarrying 63 



A complex mineral vein in the gneiss 65 



Chapter VI. — Lower Silurian sericite-schists and amphibolites on the west side of the valley. 66 



The Hoosac schist = the albitic mica-schist 66 



The Monroe area 67 



The MiddlefieUl area 70 



Section along the Boston and Albany Railroad 71 



Relation to the Becket gneiss 72 



The Granville area .' 73 



Hornblendic bands in the albitic mica-schist 75 



The Shelburne Falls anticline 75 



The Rowe schist ^ the lower sericite- or hydromica-schist 76 



Franklin County 76 



Hampshire County 70 



Hampden County 77 



Thickness 78 



The Chester amphibolite and serpentines 78 



General description 78 



Franklin County 79 



The Rowe serpentine 79 



The East Portal fault 80 



Hampshire County 81 



The Middlefield serpentine 81 



Hampden County 85 



The Chester amphibolite and serpentine 85 



The Blandford serpentines and pyroxonite 85 



The Granville and Russell enstatite-serpentines 90 



The Westfleld serpentine and marble ". . . 92 



Faults and serpentinization 95 



Petrographical description 96 



The amiihibolites 96 



The serpentines and associated magnesian rocks 97 



Bladed serpentine; antigorite- (or bastite-) serpentine 98 



