438 V. F. MARSTERS — ASBESTOS DEPOSITS OF BELVTDERE MOUNTAIN 



to them are many rod-like and acicular inclusions, the identification of 

 which, however, is not an easy matter. 



The remaining light colored silicate is epidote. It may occur as grains, 

 produced in part by crushing, or in rudely columnar masses with ragged 

 ends and irregular sides, the individuals sometimes attaining a length 

 of 4 or 5 millimeters. The maximum extinction angle observed was 11 

 degrees. 



Two cleavages are present, one parallel to the long axis and poorly 

 developed, the other a transverse parting clearly exhibited on account 

 of the rather strong refraction so characteristic of this mineral. 



Very little pleochroism is recognizable. In most cases it is colorless, 

 but occasionally a slight tinge of yellow is apparent. 



Very minute inclusions are arranged parallel to the long axis, but are 

 quite too small for specific determination. Magnetite is an omnipresent 

 accessor}', or probably a secondary product resulting from the decom- 

 position of some of the essential components. There are also present 

 small wedge-shaped or irregular grains, which behave in all respects 

 like titanite. 



LOCAL VARIATIONS 



Garnet zone. — There are certain local variations in the mineralogy of 

 the amphibolite which should be noted at this point. The exact geo- 

 graphical distribution of this feature has not been worked out in the 

 fullest detail, but so far as can be determined from the field observations 

 and collections at hand the greatest deviation from the normal type 

 occurs along the line of contact with the serpentine, best seen back of 

 the plant of the New England company and again along the fault on the 

 west side of the mountain, the position of which is indicated on the 

 geological as well as the traverse map. The former is a zone of variable 

 width, lying at the base of the amphibolite cliffs and characterized by 

 the development of a very large amount of garnet, easily detected by the 

 unaided eye, and in patches so abundant as to give the rock a reddish 

 hue. In thin-sections various stages of alteration to chlorite are evi- 

 dent. The well developed crystalline outline so characteristic of fresh 

 and unaltered garnet is largety destroyed. Such fresh grains of the in- 

 dividual as may remain are usually surrounded by rims of green to 

 yellowish-green chlorite. With it are associated small amounts of sec- 

 ondary quartz and feldspar, which permeate the cracks of the original 

 garnet and also form rims at the periphery of the individual. Indeed, 

 the alteration may be so complete that no trace of the original garnet is 

 evident, and there remains only the general outline. In such cases the 

 central portions are chiefly composed of chlorite, while the outer portions 



