118 



ON THE GEOLOGY 



crystals of white and flesh-red felspar, while the granite around deviates 

 widely into constitutional irregularities. In the neighbourhood of Nan- 

 digamah, primary limestone, chlorite schist, and white slaty quartz rock 

 appear. I could not ascertain the site in mass of the first, a clear lime- 

 stone, laminated by argillaceous matter. The chlorite occurred foliated 

 with laminar quartz, and scaly with greyish compact felspar and 

 quartz : the former variety being of the usual splendent lustre, and occa- 

 sionally tending to talcose schist. Beyond the village, hornblende and 

 chlorite schists appeared in frequent alternation, and affording rich cotton 

 moulds : the strata of hornblende were nearly vertical, while the incli- 

 nation of the chlorite was under 70° ; and a general conformity was 

 maintained, amid the frequent intrusion of granitic veins, until approach- 

 ing the western face of the Condajjilly group, which rises boldly interchain- 

 ed near Parteal: these tracts are lost in an alluvial plain. The great 

 alluvium of Ellore, extending betwixt the Deltas of the Kistna and the 

 Godaveiy, here intervenes ; and it exhibits a layer of superficial mould 

 resting upon an uniform calcareous deposit which covers an apparently 

 co-extensive bed affording the diamond, and in the neighbourhood of 

 Parteal, formerly the most productive of the jewel-bearing spots Gol- 

 coiukt. The superficial mould is fifteen feet, the tufaceous bed being 

 from five to six, and the diamond stratum of two feet in average thick- 

 ness. The obscurity attached to the geognostical history of the diamond, 

 seems rather to result from inadequate investigation in persistent geology, 

 than from the perplexed texture of alluvial connections with which it is 

 frequently associated. Its common matrix in and i^ra^jY appears 



to be a superior sandstone conglomerate, closely affined to the carboni- 

 ferous rocks, and to this series the transported alluvia which afford the 

 gem may be uniformly assigned. But while its rich depository in this 

 tract does not essentially differ in constitution from the diamond rocks of 

 either hemisphere, it is remarkable that the overlying tufaceous bed, in 

 which the gem has never appeared, is identical with it in materials, only 



