58 



GREEN MOUNTAINS IN MASSACHUSETTS. 



of quartz, which by optical investigation arc seen to have been greatly 

 strained; they have a border of broken quartz which grades into the ground- 

 mass. (See PI. x, a.) They are identical with the blue quartz pebbles 

 of the fossiliferous ( lambrian conglomerate (Vermont formation) farther west 

 (Clarksburg mountain, Stone hill). The granite pebbles are composed of 

 crystalloids of mien tcline, plates of biotite, and grains of quartz. The micro- 

 cline and quartz are crushed and faulted. Veins of a later quartz traverse the 

 fissures in the feldspars. Crystals of zircon and apatite and plates of chlo- 



i&^hkv 



Fig. 20. — Conglomerate (Vermont formation). Crest of Hoosac mountain south of Spruce bill. 



This shows ;i large cliff of the conglomerate as it occurs in place. The pebbles here are largely blue und white quartz 

 anil the cement gneisaoiu. This is in the upper half of the conglomerate horizon. 



rite occur in the feldspar. There are skeleton crystals of magnetite asso- 

 ciated with the apatite. The cement is quite similar to that of the white 

 gneiss. 



Without here going into the much disputed question of metamorphic 

 conglomerates in general, which are found in so many terranes of stratified 

 crystalline rocks, 1 it may be said that the reasons for considering this par- 

 ticular rock a true conglomerate and not a gneiss containing- peculiar con- 



1 Cf. A. Winchell, Am. Geologist, vol. 3, pp. 143 and 256. Also C. II. Hitchcock, Am. Geologist, 

 vol.3, p. 253. 



