GEOGRAPHICAL DISTRIBUTION. 63 



generally the central parts of the pegmatite masses are more acid and 

 coarser than the borders. This is well illustrated by the way in 

 which mica is found more abundantly in the outer zones of stock-like 

 masses or lenses than towards the centres of them. 



The pegmatit.es are often very coarse and not infrequently quartz 

 and felspar are intergrown in the form of graphic granite, a form 

 apparently not favourable for the .formation of good mica. The felspar 

 is, as a rule, microcline, cleavage fragments of half a cubic foot having 

 been often observed on the waste heaps. The microscope shows that 

 the glassy quartz is composed of large, interlocking individuals, usually 

 free from pressure or strain. Tourmaline, garnets, apatite, beryl and 

 columbite are prominent accessory minerals. 



Mining prospects. — By far the largest mica-crystals obtained in 

 India have been discovered in this young mining district, where the 

 pegmatite so frequently occurs in large stock-like masses. In the 

 Inikurti mine, first successfully opened by Mr. E. H. Sargent, crystals 

 of mica were found measuring 10 feet across the basal planes and 

 up to 15 feet across the folia. Rectangular sheets, perfectly free of 

 cracks and flaws, have frequently been obtained measuring 30" x 24," 

 It is difficult to predict the future of such an area : probably not a 

 tithe of the available pegmatites have been detected, and much of 

 the material may, never be found under the thick coat of laterite, 

 recent alluvium and sub-re cent sandstones, for mica is a mineral 

 which cannot be prospected for by borings. Nellore is a district in 

 which, above many others, the regulations for prospecting might be 

 advantageously relaxed without necessarily neglecting to claim the 

 full tithe of rights when actual mining commences. 



History. — Mining for mica in this district commenced in a small 

 way in 1887 when the attention of the Madras Board of Revenue was 

 called to the practice, and the Collector of the district was authorised 

 to auction the rights in specified localities for periods of two 

 years. 



The sale of the mines was delayed till September 1888, pending 

 receipt of the form of lease to be executed. Three mines, one in each 



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