302 EEPORT OF NATIONAL MUSEUM, 1899. 



it is soft, fine and silky, otlier portions are characterized by a harshness or stiffness 

 which detracts greatly from its commercial value. 



The veins while not disturbed by faulting generally improve so far 

 as quality of material is concerned as the depth below the surface 

 increases. They are, however, very irregular in their distribution, 

 and are rarely persistent for any great distance. 



A small vein at the surface, of half an inch in thickness, may quickly enlarge to one 

 of three inches or more, and, continuing, may die out entirely, while others come in 

 on either side. They have much the aspect of the gash veins in slaty rocks, though 

 there are many instances seen where the fiber maintains a tolerably uniform size 

 for considerable distances. [See large Specimen No. 61348, U.S.N.M.]. 



Fig. 11. 



SERPENTINE ASBESTOS IN MASSIVE SERPENTINE. 



Specimen No. 72836. 



The containing rocks show the presence of numerous faults, as m other mineral 

 localities, but possibly in the serpentine these are often more plainly marked. These 

 faults throw the veins from side to side, and frequently are of sufficient extent to 

 cut off entirely the working face of a highly i)roductive area, the rock on the other 

 side of the fissure being often entirely barren. The sides of the fault, in such cases, 

 show extensive slickensides, and frequently have great sheets of coarse or woody- 

 fibered or imperfect asbestos, along the planes of fracture. Occasionally, pockets or 

 small veins of chromic iron are found in close proximity to the asbestos.' 



Specimens Nos. 62135, 62150, U.S.N.M. from Marmora and Thetford 

 show the characteristic manner of the occurrence of the mineral on a 

 small scale, while No. 62151, U.S.N.M., shows the material as freed 

 from the wall rock, before shredding. See also Specimens Nos. 53682 

 to 53690 from Danville, Province of Quebec. 



' R. W. Ells, Transactions of the American Institute of Mining Engineers, XVIII, 

 890, p. 322. 



