HOOSAC MOUNTAIN. 



53 



Quartz occurs sometimes in large rounded masses, greatly strained and 

 shattered, and surrounded by a mosaic of small quartz grains. Large pieces 

 of microcline occur, faulted and broken, the cracks filled with an aggregate 

 of little quartz grains and feldspars in simple twins. (See PL vn, r>.). The 

 groundmass of the rock is a closely interlocking aggregate of quartz grains, 



Jff 



Fig. 17— Metamorphie conglomerate (Vermont formation). Bump. Centr.nl shaft. One fifth natural size. 



The figure represents the banded variety of the rock, in which we find it difficult i" draw the linehetwecntrne pebbles 

 and forms produced uj crushing. A glance at the figure, especially at the right side, shows that the extremely pointed ends 

 of some "i the apparent pebbles must be produced by the encroachment of the mica layers. Vet these white masses have 

 a lithological character different from that of the "cement,' 1 forming, for instance, the broad band near the rightside. The 

 former are a tin.- -rained -ran it '■ or u r rauulitt\ sometimes blue quartz ; the latter a coarser -rained mixture of quartz, mica. 

 anil some feldspar. 



little feldspar grains simply twinned (if at all) and often little grains of 

 microcline of the same form and size. Epidote is often present in large 

 quantities, forming microscopic yellow bands in the rock, and inclosed in 

 the feldspars and micas in little prisms and grains, but not in the quartz. 



