LADAKH, NORTH-WESTERN HIMALAYA. 317 



a feeble double refraction and has the refractive index of serpentine. 

 In converging polarized light I could get no definite results even with 

 a -^ immersion lens in oil. This fibrous serpentine generally sur- 

 rounds remnants of corroded augites and is evidently the product of 

 the decomposition of large crystals of this mineral. (Figs. 4 and 5, 

 Plate 18.) This conclusion is confirmed by two observations. The 

 first is that a large augite (Fig. 5, Plate 18) is penetrated by solu- 

 tion veins which are now filled with the fibrous serpentine and 

 this is continuous with the fibrous serpentine in which the augite 

 is imbedded. The veins widen out towards the margin of the augite 

 like the mouths of rivers, and the fibrous serpentine in them passes 

 into the fibrous serpentine outside without a break of any kind. 

 The second fact is that though the fibrous serpentine has gener- 

 ally straight extinction, I have observed one or two cases in which 

 the extinction is oblique. The latter fact seems to indicate that the 

 serpentine was derived from a monoclinic pyroxene, but that its 

 conversion in some cases was not quite complete. 



This fibrous serpentine is I think a variety of chrysotile. 



No. 82—94. Serpentine, from the valley west of Sirsa La, Zanskar ; collected 

 by T. D. La Touche. 



The two hand-specimens consist of serpentine with a vein of 

 white soda-zoisite running through it. 



The dark portions of the hand-specimens are composed of ser- 

 pentine with allo-triomorphic crystals of enstatite and magnetite 

 imbededed in it. No eyes of olivine remain. 



The following note was made by Mr. F. R. Mallet, F.G.S., F.C.S., in 

 the Calcutta Geological Survey Laboratory book, p. 129, under date 

 19th January, 1889: — 



"Sp. G. 3*442 (Mr. Blyth) 

 H. 7. 



Fuses easily to a blebby bead with strong intumescence. When 

 treated for two and a half hours with strong hydrochloric acid 61*2 



( 15 ) 



