114 q[Jicksilvp:r deposits of the tacific slope. 



pentines of the Coast Ranges. The Swedish serpentine, however, is stated 

 to be sensibly uniaxiul, which, as Eichstadt remarks, perliaps means only 

 that the angle of divergence of the optical axis in this case is extremely 

 small. It seems doubtfnl whether the isotropic mineral referred to by 

 Messrs. Fouqu^ and JMichel-L^vy can be the same as that of the Coast 

 Ranges, 



Microstructure of the serpentine. — Of tlic many vaHetics of Serpentine which 

 have received separate mineralogical names several are recognizable mac- 

 roscopically in the Coast Ranges. The most ordinary is the massive 

 green mineral of different shades usually intersected by highly polished, 

 curved surfaces. Such rock is often traversed by narrow veins of white or 

 light-green, fibrous chrysolite. Marmolitic modifications are also abundant 

 In many of the serpentines dark, rounded scales are frequent, and these 

 often show in some lights a metallic luster answering to bastite or schiller- 

 spar in jjart. 



Under the microscope there are found to be great differences in the 

 structure and arrangement of the gi'oups of fibers or scales of which the 

 serpentine is built up. These are sometimes felted, but more often united 

 in bundles of approximately similar orientation. In the latter form they 

 answer to the descriptions of antigorite. Xot infrecpiently groups of scales 

 are seen under the microscope, forming masses of considerable size, in wliich 

 the orientation is substantiall}' uniform, and in sections cut obliquely to the 

 predominant cleavage of these masses a fine, yellow, metallic luster is some- 

 times observable once in every complete revolution. It is uncertain to 

 what this luster is due. These masses are of course the so-called bastite 

 scales. There are, however, many other asfgregates similar in all respects 

 excepting that they show no metallic luster. Tlie groups of parallel foils 

 are sometimes separated from the surrounding mass by sharp lines, which 

 in no case present crystallographic outlines, but often the demarkation is 

 not sharp. 



The mineral of wliich the antigoritic, chrysolitic, and bastitic aggre- 

 gates are built up appears to be essentially the same, and in no way differ- 

 ent from that of the felted aggregates. It corresponds well to the descrip- 

 tions of antigorite, but answei'S equally well in all essential particulars to 



