158 PERIDOTITE. 



senting the portions of the olivine last altered. In some portions the section is filled 

 with reticulated veins of brown and cherry-red hematite. The dark spots are owing to 

 portions being filled witli innumerable granules of iron ore, arranged about some central 

 lines, much like iron filings about the poles of a magnet. Talc fibres are common. 

 Chrysotile veins cut the section in various directions. 



From trail below Chip Flat, Sierra Co., Cal. 



45 P. The specimens are green and more or less rubbed or " slickensided," as are the 

 great majority of serpentine rocks. The only section is of a pale yellowish-green color 

 traversed by black bands of iron ore. The serpentine .shows a coarsely aggregate and 

 fibrous polarization, and appears from its structure to replace, in part at least, olivine and 

 enstatite. The ore crystals are octaliedrons, some of which are translucent either as a 

 whole or on the edges. The translucent portions are reddish-brown, and the opacity 

 does not seem to depend upon the size, since some comparatively large crystals are 

 translucent, while very minute ones are often opaque. 



40 P. Similar to the preceding. This rock occurs apparently in two bands, enclosing 

 slate, according to the collector. Professor W. H. Pettee.* 



119 P. is of similar character. In the interior it is compact, massive, and dark, but 

 on the exterior smoothed and coated with greenish and light greenish-yellow serpentine. 



Depot Hill, near Camptonville, Sierra Co., California. 



35 P. A compact greenish-gray rock with irregular bluish-black spots, and traversed 

 by chrysotile veins. 



Section : a compact grayish and greenish-yellow mass, composed principally of ser- 

 pentine with iron ore, and dolomite. From the structure of the serpentine and the 

 arrangement of the iron ore, it is probable that olivine and enstatite were former con- 

 stituents of this rock, which was only found in a boulder.f 



From a belt four hundred feet wide, between Whislcey Diggings and Hcpsidam, 



Plumas Co., California. 



89 P. A bluish-black and greenish mottled rock, showing a reticulated structure. 

 It is traversed by yellowish-green serpentine veins. 



Section : a gray groundraass spotted by magnetite and traversed by veins of magne- 

 tite and yellow serpentine. The groundmass lias been so entirely changed to serpentine, 

 showing the usual network structure, that none of the original silicates were observed. 

 So far as can be judged from the structure, the rock originally contained olivine and 

 enstatite, at least. Figure 5 of Plate VI. shows its present structure and the serpentine 

 veins wlftch traverse it. J 



Finland. 



According to Lagorio, the Finland serpentine forms a fibrous mass of yellowish-gray 

 to green color, showing the usual network (Maschenstructur). It contains no olivine 

 grains, but some fissured ones of dolomite or calcite. The microscopic structure is very 

 finely fibrous, and it forms masses in a limestone. § 



» Aurif. Gravels, p. 434. f Ibid., p. 429. % Ibid., p. 451. 



§ Micro. Analyse Ostbaltischer Gobirgsarten, 1876, p. 48. 



