HOOSAC MOUNTAIN. 



49 



second narrow belt occurs near the West Portal, adjoining the Hoosic 

 valley (Stockbridge) limestone. On the surface it occupies a large area, 

 especially in the southern part of the held. The quartzites occur generally 

 in or near the Hoosic valley adjacent to the limestone, associated with 

 conglomerates and passing along the strike into the granulitic and gneissic 

 rocks by increase in the amount of feldspar and mica. 



r 



FIB. L4.— Metamorphic conglomerate (Vermont formation). Dump, Central shaft. Two-ninths natural size. 



The larger pebbles are mostly gn lite, with some of lilm- quartz and feldspar. This shows v-erj plainly the shape "I 



the pebbles, which are but little elongated in the plane normal to the picture. 



Beginning with the simplest rocks, the quartzites, there are vitreous 

 varieties and crumbly feldspathic varieties passing into gneiss. The 

 vitreous variety occurs in large masses with verv obscure stratification, 

 and roughly jointed. It varies in color from snow white to yellow, contains 

 often layers of mica and cubes of pyrite. The microscope shows an even 

 mon xxiii -A 



