. Bulletin of the Geological Society of America. Geology. 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 f
. Bulletin of the Geological Society of America. Geology. 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 l
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