124 QrrcKSiLVER deposits of the pacific slope. 



original mass is now entirely occupied by felted fibers of serpentine, and 

 long, slender microlites pierce the quartz grain toward its center like pins 

 in a cushion. That there might be no doubt as to the con-ect interpreta- 

 tion of this important case another quartz was selected in the same slide, 

 wliich showed the same phenomena, though less beautifully. Tliis was 

 tested by chemical methods, as described on page 112, and the green min- 

 eral was proved to be a silicate of magnesium, attackable by chlorhydric 

 acid. The serpentine wliich was chemically tested in this second case was 

 absolutely indistinguishable in color, texture, or behavior in polarized light 

 from that suiTounding the quai-tz shown in the figure, and the distance of 

 the two occurrences from each other v.as only about 3""". The long mi- 

 crolites wliich pierce the quartz are of the same color as the strip of ser- 

 pentine occupying the periphery of the section. Their optical properties 

 cannot be well observed, because they are embedded in the brilliantly 

 polarizing quartz, but there appears no reason to suppose that they differ 

 chemically from the serpentine at their bases. Even if they belonged to 

 another mineral species, however, tlie structm-e is such as to show that they 

 must be regarded as an intermediate product between quartz and the sm-- 

 rounding serpentine, which would make little difierence from a geological 

 point of view. 



Apatite is found in process of conversion to serpentine in specimen No. 

 107, Sulphur Bank, one of the specimens in which t]:e presence of authi- 

 genetic apatite was proved by chemical as well as by optical means. The 

 apatite crystals embedded in sei-pentine in this slide are seen to be cor- 

 roded and the indentations are' occupied by serpentine. As already men- 

 tioned, Professof Dana has observed psendomorphs of serpentine after 

 apatite. 



There are also a number of cases in which chlorite appears to be 

 altered to serpentine. Thus in specimen Xo. 266, Sulphur Bank, a chlorit- 

 ized pseudodiabase, areas of chlonte are intersected by cracks, along the 

 walls of which serpentine is disposed in such a way as to lead to the belief 

 that the latter mineral is ejiigeuetic ; but, as in the case of the conversion to 

 epidote, the fibrous character of the chlorite somewhat weakens the evi- 

 dence obtainable from observation. Bischof regarded the serpeutiuization 



