44 EOOTE : GEOLOGICAL STRUCTURE OP THE EASTERN COAST. 



Small irregular granite veins of pale pink colour and coarsely crystal- 

 line texture are common in the micaceous and hornblendic schists south- 

 east of the Chimakurti mountains, but they offer no points of special 

 interest. 



c. — Felsite veins. 



A small series of hard vein-like bands of light coloured rock, having 

 considerable resemblance externally to quartzite, traverse the hornblendic 

 gneiss south-west of Pothakamur (Poothkamoor of sheet 76). 



These veins— for such they undoubtedly are— as they cut across the 

 beds of gneiss at an angle of 45°, consist of compact felsite of pale 

 bluish-grey colour, weathering a very pale cream colour. The freshly 

 broken surfaces of unweathered parts of the rock show here and there 

 sections of flesh-coloured crystals of felspar. The veins are small, being 

 only 3 to 4 feet thick, and exposed only in short lengths. They occur 

 over a tract about 2 miles long by a mile in width, which they traverse 

 in a north-east to south-west direction. Though tolerably numerous, the 

 veins form an inconspicuous feature in the landscape, and might be easily 

 passed by unnoticed. 



No other occurrence of felsite rocks was observed in the Guntur- 

 Ongole region. 



d. — Quartz veins. 



Quartz veins are numerous only in parts of the gneissic area, but, like 



the granite veins and trap dykes of this region, they are, with but few 



exceptions, of very small importance and size. The most remarkable 



exception is a considerable mass of quartz on the south side of the faulted 



„ southern boundary of the anticlinal ellipse west 



At Nakarikalm. _ '- 



of Nakarikallu, at a spot close to the intersec- 

 tion of the meridian of 80° east longitude by a parallel drawn in latitude 

 16° 20' north. Though covering a large surface, the relations of the 

 quartz to the fault are obscured by debris and soil, and it does not show 

 any characteristics of being a fault rock, as might very well be inferred 

 from its position. 

 ( 44 ) 



