426 V.F. MARSTEKS — ASBESTOS DEPOSITS OF BELVIDERE MOUNTAIN 



the literature suggests that the Vermont series may be the late Cambric 

 or early Ordovicic in age. 



AMPHIBOLITES 



Areal distribution. — An inspection of the map of the Belvidere region 

 will show that the main area of amphibolite is confined to the uppermost 

 1,000 feet of the mountain crest at the southern terminus of the ridge. 

 This rock probably makes up the tip of the ridge as far as Hazens 

 notch ; how far it may extend beyond has not been determined. 



Small but important exposures of the same rock occur at the lower 

 edge of the serpentine and in prospects opened up by Judge Tucker. 

 There are thus three areas; but the two smaller ones are particularly 

 important, inasmuch as they provide certain data which it is believed 

 will make clear with reasonable certainty the true lithological relation- 

 ships of the amphibolite and the serpentine and the origin of the latter. 



At the south end of Belvidere the amphibolite forms the steep sloped 

 portion above the plateau-like terrace, as seen in the accompanying 

 illustration (plate 73, figure 1). 



Macroscopic characters and mineral composition. — A very large portion of 

 the rock is composed of dark-green hornblende, so arranged with respect 

 to the cleavage of the individual components that a gneissic and, at 

 times, a decided schistose structure is fairly well defined. At the base 

 of the hornblendic mass, or just above the level of the rimming plateau 

 referred to, the amphibolite presents an additional phase in becoming 

 highly garnetiferous. The relation of the garnet-bearing zone to the 

 underlying serpentine is not easily determined, as the probable contact 

 is covered by waste from the cliffs above. At a few points in the rear of 

 the plant of the New England company garnet was recognized as high 

 as 70 feet above the foot of the talus slope. So abundant is the garnet 

 at various points along the base of the cliff that the rock assumes a 

 marked reddish color, and thus, at first sight, might be regarded as 

 quite distinct from the normal amphibolite. From this point upward 

 the garnet gradually disappears. Above the 70-foot mark (barometric 

 determination) it could not be detected in any of the hand specimens 

 with the unaided eye. The microscope, however, reveals the fact that 

 garnet does occur in small amount above this height. The main mass 

 is nevertheless confined to the base of the amphibolite, and probably 

 represents a local contact phenomenon. Its extent, so far as known, is 

 indicated on the map of the Belvidere region. 



The texture of the normal amphibolite is quite variable. At the top 

 of the ridge it is a fine grained mass, with occasional bands of feldspathic 



