1840.] 



of the Great Basaltic District of India. 



63 



varying very much in colour, composition, and appearance in different 

 places. Above Bangnapilly it contains the diamond breccia described 

 by Voysey. As far as the shafts which I had an opportunity of observ- 

 ing, enabled me to judge, the breccia is not an interstratified rock, but 

 an intermixture of the common sandstone, in different parts of the same 

 stratum, with larger fragments of older rocks, generally rounded but 

 sometimes angular. It is not, however, the object of this paper to des- 

 cribe the mines and the interesting district in which they occur further 

 than is necessary to exhibit the type of the formation, by the study of 

 which I was enabled to understand more clearly, the less distinct appear- 

 ances exhibited by the same rocks, where they have been invaded or 

 buried by the great basaltic eruptions of Central India. On the opposite 

 or west side of the valley, the hill is composed of the same argillo- 

 calcareous formation ; but, according to Colonel Cullen, " instead of a 

 sandstone cap, it is crested in its whole length with a sharp black ridge 

 of trap rock, formed of loose blocks piled upon each other, the apparent 

 base of which observed a pretty uniform level, nor is the ridge of much 

 depth. Its extreme narrowness, deep black colour, and the total absence 

 of all traces of vegetation, formed a singular contrast to the rest of the 

 hills, which were covered with long dry grass and scattered bushes*." 

 At a small pass some miles further to the west, the road in ascending, 

 passes over first the dark limestone and a narrow belt of schist, then 

 trap, which is again succeeded by limestone, and the latter by schist, 

 nearly to the summit, " which is capped with a rock of a beautiful flesh 

 colour, with specks and shades of a beautiful green, as if connected with 

 its vicinity to the trap, and of so close and fine a texture as to appear 

 homogeneous even with a lens." " The descent of the pass on the 

 opposite side consists of a clay slate nearly to the foot, where the lime- 

 stone reappears, and these two rocks continued to alternate with each 

 other to the foot of the second Ghat, which, like all the former, was 

 composed of clay slate capped with quartzose sandstonef ." 



The sandstone exhibits many varieties of grain, colour, and hardness : 

 in some places it is white or red, and can be cut into pillars and slabs 

 of great size and beauty ; in others it is soft and friable, and its inferior 

 beds are not unfrequently schistose, so as to be with difficulty distin- 

 guished from the subjacent rock, with which it has in one or two places 

 been observed to alternate. Where the sandstone approaches the great 

 granitic tracts to the south and west, it passes into a compact quartzose 



* Colonel Cullen, in Transactions of the Literary Society of Madras, January 1837 

 p. 50. + Ibid, 



