132 G. P. MERRILL — ORIGIN OF VEINS IN ASBESTIFORM SERPENTINE 



approximately vertical veins (some 30 millimeters in maximum diame- 

 ter), it is to be noted that they are often branched, and that, further, the 

 branches are sometimes smallest at their point of attachment. At first 

 glance, these vertical veins appear to be cutting across the horizontal. In 

 reality such is not the case ; with possibly one exception each and all 

 fray out — that is, split up abruptly into a number of small veinlets, 

 which terminate before reaching the larger. This feature is not readily 

 apparent in the plate, owing to the half-tone process used in reproduc- 

 tion, but is easily seen in the photograph, and better yet in the specimen. 

 In a single instance (see A in plate 33) the appearance is as if the vertical 

 vein had at one time been continuous above and below the horizontal, 

 but had been pinched out by some subsequent movement of the mass. 

 Although not well shown in this particular specimen, these veins, as is 



Figure 1.— Feins on opposite Sides of Serpentine Block. 

 Shading represents veins, white portion serpentine. 



well known, are never continuous for any great distance, but pinch out 

 to mere knife-like edges at the ends, or are variously forked and frayed, 

 as indicated in the drawings in figures 1 and 2. A common and abrupt 

 change in the form of the veins is shown in figure 1, representing a block 

 of serpentine some 8 by 10 by 3 centimeters in thickness, and showing 

 the same series of veins as they appear on opposite sides of the block. 

 In all cases the vein material separates readily from the massive, in- 

 dicating that the fibrous portions originated through crystallization in an 

 open fissure, though it does not necessarily follow that the fissure was 

 open to its present width when the filling process began. 

 * Referring to the fibers themselves, it may be stated that they are soft, 

 tough, and pliable, with a silk-like sheen or luster. In cross-section they 

 are flattened or cylindrical, in this respect in strong contrast with the 



