THE CHESTER AMPHIBOLITE AND SERPENTINES. 85 



serpentine, to a deptli of lO-lS""", acuompauied with loss of color, hardness, 

 and volume; and as a result of this last the surface is often covered with 

 a fine system of regular shrinkage joints, one set of straight fissures about 

 20"""' apart being cut by another at an oblique angle, the latter about 

 50™° apart. In places the blocks have all separated from the underlying 

 unchanged mass and lie loosely upon it. 



HAMPDEN COUNTY. 



THE CHESTER AMPHIBOLITE AUD SERPENTINE. 



Following the heavy hornblende band across Chester, where it forms 

 in the north the high, sharp ridge called Gobble Mountain, and in the south 

 the still higher Round Mountain, one finds in the higher part of the first 

 hill a considerable deposit of serpentine (bed No. 7), situated, like the others, 

 at the upper surface of the hornblende, but ofi'ering nothing peculiar. 

 Farther south, in the bottom of the brook gorge between these hills, at 

 the old emery mine, is another deposit (bed No. 8), which is at a level of 

 several hundred feet below the other. 



The excavations at the mine exposed the following section from east to 

 west across the vertical strata: 



Section at the old emery mine near Chester. 

 Savoy schist Sericite-schist. 



^Steatite inclosing a few small serpen- 



I tine nodules 4_16 



Chester amphibolite . . < Emery and magnetite bed 6i-10 



I Fringe rock 1 inch to 10 



vHornblendeschist. 



The small nodules of serpentine, often as large as one's hand, are 

 isolated in the mass of the talc and are permeated by veins of the same 

 material, and doubtless represent the original material from which the talc 

 was formed. The serpentine is the usual variety, dark-gi-een when wet, 

 but, partly from its fine splintery fracture, gi-ay-green when dry. Another 

 variety is rich olive-green, and can-ies much malachite. 



The talc is pale-green, fohated for the most part, and often crowded 

 with dolomite crystals. 



THE BLAXDFORD SERPENTINES AND PYROXENITE. 



The heavy hornblende bed continues with undiminished width across 

 Chester, and is much covered by di-ift as it crosses into Blandford, where it is 



