SINO-MONGOLIAN FRONTIER 



basalt of a dark grey colour, not unlike that en- 

 countered in Shansi, while in the valley leading 

 up to it various kinds of rock, all igneous, were 

 noticed. Amongst others, we gathered specimens 

 of a red-brown porphyry containing numerous 

 elongated air-holes, besides distinct crystals of 

 felspar and quartz. Specimens of metamorphosed 

 felspar, of light grey basalt, and of a peculiar 

 yellow sandstone, were also gathered. The pre- 

 dominating rock throughout, however, was found 

 to be basalt, and, nearer to Kalgan, trachyte. 



Except in the hills and on the ridges of the 

 Plateau, the thick grass-covered surface soil pre- 

 vented our noting the nature of the sublying 

 rock, but an examination of the outcrops in the 

 hills showed that basalt greatly predominated, 

 while dykes of granite occurred here and there. 

 As we approached Lama Miao the granite in- 

 creased in proportion till it seemed, sometimes, 

 as if dykes of basalt crossed the general mass of 

 granite. Usually, however, the higher ridges 

 were found to be of granite, while wherever the 

 sublying rock in the lower slopes and valleys was 

 visible it usually turned out to be basalt. At a 

 place named Oola Hutaga some gneiss was noticed, 

 but here also the hills were chiefly of granite and 

 volcanic rock. 



At Tabool we noticed some wide veins of quartz 

 running north and south through metamorphic 

 and granitic rocks. This quartz was not noticed 



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