GEOLOGY OF THE AREA. 13 



of pure quartz occurring in the gneiss. On the road from Wandur 

 to Nilambur, between the nth and 12th milestones (which count 

 from Pandikad), what appears like a quartz reef rises through the 

 laterite. Its direction is 5 E. of S. This being the direction of the 

 lamination of the neighbouring gneiss, it is probable that this 

 apparent reef is only a bed. 



Shortly before the Wandur-Nilambur and the Eddawannah- 

 Nilambyr roads meet, there is, on the east of the former, a low 

 jungly hill, the rock of which is almost pure quartz. Just before 

 reaching Nilambur, there is again another hill (on the west side of 

 the road) with a large band of quartz. 



If we go east from Wandur towards the Silent Valley, we again 

 meet with large beds composed of nothing but quartz. They always 

 run in the strike of the gneiss, and are beds, not reefs. Small veins 

 of quartz are very common, but none of large size were met with. 



Large masses and runs of hornblendic rock are not uncommon in 



the quartzose gneiss, especially in what appears 

 Hornblendic gneiss. ^ & > r J rv 



to be the upper part of it. Most of the rock 



near Nilambur is highly quartzose ; but what is known as Nilambur 



Hill is very hornblendic. About 3^ miles north-east of Nilambur, on 



the Karkur road, is another mass of hornblendic gneiss ; and near 



the banks of the Shaulay-ar of the map (east of the letters au) the 



rock is compact hornblendic gneiss. The hills near Eddawannah 



are largely composed of similar rock. 



These are the most important occurrences of large masses of the 

 compact hornblendic gneiss. But small runs resembling dykes are 

 very common. In the valley of Chatalur, south of the Chikmala 

 ridge, there are four running 15 — 50 S. of E. The rock is not 

 precisely the same as that of the large masses ; and it is probable that 

 these runs are truly eruptive. 



The haematite gneiss is another variety occurring in the midst of 



the quartzose series. About a mile and a half 

 Iron-bearing gneisses. 



south-west of Nilambur is a little group of jungly 



hills, the most southerly of which is partly composed of schistose 



( 213 ) 



