116 KHASI HILLS. 



and occasionally in greater abundance ; but in most of these cases, the 



additional hardness of the rock would prevent this ore from being 



extracted with as much economy from the slates, as from the granite. 



I have not been able to trace the existence of any organic remains 



^ , , . , whatever in these rocks. They are, as far as I 



''^°^'^' know, throughout the entire group, truly azoic. 



There would, however, appear to be two very distinct groups of 



these metamorphic rocks, differing materially in 



Two groups. „ , . 1 ■ 1 1 1 



the amount ot alteration to which they nave 

 been subjected, and also in the variety in composition and character 

 which the beds exhibit. The older and more altered group of these 

 is represented by the highly crystalline gneiss, quartzite, &c., of the 

 valley of Cherra and other places. These, as I have already described, 

 consist of alternating beds of gneiss, quartzose schists, and quartz, greatly 

 contorted, and traversed in every direction by veins of finely crys- 

 talline granite. With these are also associated occasionally beds of 

 hornblendic rocks. 



On the other hand, the upper group, which is quite unconformable, is 

 essentially slaty, consisting of blue and grey flaky schists, with some 

 micaceous and quartzose layers. These are also disturbed, but not to 

 the same extent as the gneissose beds below, and, although occasionally 

 granite veins are found piercing them, these veins are by no means 

 numerous or large. Unfortunately nothing organic has as yet been dis- 

 covered in these rocks to give evidence of their age. In liihological 

 aspect they have many resemblances to the Lower Silurian slates of 

 Europe, but this resemblance is of no value whatever in fixing their 

 date. To an Indian Geologist, the two groups may be more readily 

 described as representing, the lower or gneissose group, that of Bengal 

 Proper, and the upper or slaty group, that of the Sikkim Himalaya 

 (Daijiling). The latter is in all probability the representative of, or 

 on the same geological horizon as, the metamorphic rocks of the Ner- 



