304 McMAHON : PETROLOGICAL NOTES ON SOME PERIDOTITES, ETC., 



From their dark colours these rocks have sometimes been referred to 

 as basalts, but they have certainly nothing to do with these more 

 recent volcanic rocks. At first coming to the camp on the Puga stream 

 we met with an epidote rock, consisting of crystallized or granular 

 masses of epidote, quartz and albite. The epidote when crystal- 

 lized occurs in short prisms of yellowish or bright green colour. 



It is often replaced by diallage occurring in the same manner in 

 short laminar prisms and forming a beautiful syenite-like rock. 

 Somewhat farther to the north the epidote disappears altogether, 

 and the diallage is often found disseminated through a dark green 

 serpentine mass, and in this way forming a very peculiar rock which 

 by many geologists, especially in the Apennines and Southern Alps, 

 would be called gabhro ; the Himalayan agrees exactly with the 

 Alpine rock. Diallage occurs besides in large lumps, and very 

 seldom is any bronzite to be seen here. The serpentine rock 

 contains also sometimes sparingly zeolitic and felspathic minerals, 

 and varies greatly in colour. Further to east it is occasionally to be 

 found in serpentine-schist and purer in thin veins. In the Puga 

 valley itself no stratification whatever is perceptible in the whole 

 series of these last-mentioned rocks : they have a truly massive 

 structure. 



What is still remarkable and perhaps worthy of notice are large 

 spheroidal masses of quartz, which, in addition to numerous quartz 

 veins occur throughout the serpentine rock. " 



The following specimens collected by Dr. Stoliczka are described 

 in the following pages :— • 



No. 94 — 210 * Gabbro from the Puga valley, Ladakh. 



„ 94 — 211. Gabbro from the Puga valley, Ladakh. 



„ 94—313. Peridotite (Lherzolite), Makha river, Ladakh. 



„ 94 — 214. Peridotite, Puga valley, Ladakh. 



„ 94—215. Peridotite (Saxonite), Puga valley, Ladakh. 



„ 94 — 216. Serpentine after picrite, Puga valley, Ladakh. 



„ 94—225. Serpentine, from Hanli (Rupshu). 



* The numbers given in this paper are those borne by the specimens in the Geological 

 Survey Museum, Calcutta. 



( * ) 



