436 V. V. MAKSTERS — ASBESTOS DEPOSITS OF BELVIDERE MOUNTAIN 



central line or whether the fiber develops simultaneously along its en- 

 tire length is not easily demonstrated. If the latter were true and the 

 deposition of the ores were cotemporaneous with the growth of the fiber 

 we should not expect to find a tendency toward central localization of 

 the metallic contents, for the chances for uniform deposition at all points 

 within the crevice would be equally good. It is true that such condi- 

 tions can be found, but do not conform to the general plan observed. 



On the basis of the first hypothesis, if we assume that the fiber began 

 its growth on the walls of the fracture and pushed its way toward the 

 center, then we should expect an increasing amount of ore deposition in 

 the central portion, with the infringement of the fiber from the sides. 

 As a matter of fact the ore does, in the majority of cases seen, favor a 

 central position, as if the circulating waters which carried the ore were 

 compelled to move in a central zone. It follows, then, as a consequence 

 of this sort of growth that a coalition and knitting together of the oppos- 

 ing ends as they came in touch should result. Moreover, it would seem 

 that the line of juncture should be detected in cross thin-sections, for it 

 would be most remarkable that the growth of opposite individuals or 

 strands should have the same optical orientation and unite in such a 

 way, where not interfered with by the deposition of iron ore, as to appear 

 to be one and the same individual. In the few sections at hand I have 

 not been able to detect this relationship, but it is believed that further 

 study of the problem may show that this interpretation is in the main 

 the correct one. 



It might be said that the deposition of the ores was subsequent to the 

 growth of fiber and along secondary fractures within the body of the 

 latter. It is true that the fiber-bearing veins have been sheared, for it is 

 this process that has produced the slip-fiber. This supposition may be 

 true, but it still remains that veins which do not show any evidence of 

 shearing or fracture also contain much magnetite in central partings or 

 as rods and bunches parallel the strands ; hence in such cases there was 

 no opportunity for the subsequent deposition of the ore. While it must 

 be admitted that sufficient material and data are not at hand to solve 

 the problem, it is believed that such facts as we have favor the interpre- 

 tation as expressed in the above hypothesis. 



Amphibolite 



micro-structure and mineralogy 



In the predominant type of amphibolite hornblende is far in excess of 

 all the other constituents combined. It makes up from 70 to 90 per cent 

 of the entire mass. In thin-section the hornblende appears as large in- 



