12 KING : COASTAL REGION OF THE GODAVARI DISTRICT. 



CHAPTER II.— GNEISS AND LOWER GONDWANA EOCKS. 



The Bezvdda gneiss. — Notwithstanding the more rapid and general 

 survey of the area o£ crystalline rocks, enough was observed of them to 

 justify the recognition of a particular variety or sub-division which 

 other observers besides myself had noticed, more especially in the 

 neighbourhood of Bezvada and on the Vizagapatam coast. It might 

 be called murcJiisonite gneiss from the characteristic form of felspar 

 entering so largely into its composition, which mineral was, however, 

 eventually recognised by my colleagne, F. R. Mallet, in the specimens 

 which were sent up to him for determination at Calcutta. 



Dr. Heyne noticed the garnetiferous and felspathic constitution of 



„ . ! , ,„ the rock and its tendency to weather of a dark 

 Previous knowledge J 



of — or even nearly black colour ; writing of it : " Veins 



of felspar often run through this rock in oblique or horizontal direction. 

 Such veins are much harder than the felspar, which enters as a constitu- 

 ent into the rock. * * * The felspar is white, foliated, and appears, when 

 in large pieces, transversely striated. It is uncommonly soft, and is 

 entirely disintegrated when long exposed to the air/' 1 Dr. P. M. Benza 

 describes, 2 but not in much detail, the gametic gneiss of Bezvada, and 

 he saw it again at Tiini and other places in the Vizagapatam district ; 

 the felspar is specialised as albite or cleavlandite, and its beautiful scarlet 

 red colour is noticed. He also refers to the easily- weathered character of 

 the rock. Captain Newbold wrote — C( The gneiss comprising the ridge 

 of Bezwada is garnetiferous, cleavlandite often replaces the common 

 felspar, and renders the gneiss liable to decay. It contains large veins 

 of quartz and is intersected by green-stone dykes, the presence of which 

 may serve to account for the distortion observable in its strata." 



A decided band of this garnetiferous felspathic gneiss edges the 



Extent and relation to alluvium and older aqueous rocks right across the 



other gneiss. field ^ from the Kistna district into that of Vizaga- 



( 206 



1 Op. cit. p. Tract XV, p. 230. 



2 Op. cit. p. 45. 



