GEOGRAPHICAL DISTRIBUTION. 65 



Nilgiris. 



Mica-bearing pegmatites occur at numerous localities in south-east 

 Wain ad, 1 the chief localities hitherto recorded being — ■ 



Gudalur. 



Devala. 



Nellakota. 



Pandalur. 

 Cherambadi. 



The best mica has been found in the neighbourhood of Cherambadi, 

 where it is being mined by Mr. W. Morres on Naiken Shola and by 

 Mr.W. MacKinlay on the Llewellyn Estate. Fairly large sheets of 

 good quality have been found at the other localities, mostly, however, 

 on the surface, and further prospecting will be necessary before their 

 value can be determined. 



At Cherambadi the mica is ruby-coloured of high quality, and occurs 

 in considerable masses in the pegmatite-veins with quartz and felspar. 

 Accessory minerals are very rare, only garnet and biotite having been 

 identified. The trend of the veins corresponds with the strike of the 

 foliation of the country rock, and is usually east-north-east to west- 

 south-west, crossing the strike of the auriferous reefs at a high angle. 



In all the pegmatite veins examined there is a peculiarly similar 

 and persistent grouping of the constituent minerals. The quartz 

 occurs in great wall or dyke-like masses, while beside it are masses of 

 almost quartz-free felspar usually altered to a very pure, white kaolin. 

 Between this kaolin and the quartz, the mica occurs in large " books," 

 frequently found adhering to the quartz. The mica and felspar occur 

 as a rule only on one side of the quartz (fig. 16). 



The total thickness of the pegmatite bands seldom exceeds eight 

 feet. 



1 This account of the mica-bearing localities in the Wainad is by my colleague 

 Mr. H. H. Hayden {see also General Report, Geological Survey, India, 1899-1900, 

 pp. 56 and 57J. 



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