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Yol. 57.] OF SOTJTH-CEiVTRAL CEYLON. 199 



contain little or no quartz. These bands often have a wavy habit, 

 as though torn, and sometimes small black patches, like fragments 

 of bands, appear isolated in the more granitic rock (see fig. 2). 

 Rather frequently we find large felspars rounded in outline, and an 

 inch or more in diameter. In 25 to 30 yards a very hornblendic 

 rock crops out, followed in turn by one conspicuously banded. We 

 ^nd next the hornblendic rock veined by the granitic : some of 

 the veins are only 



•5 inch across. Fig. 2. — Banding in gneissoicl granid'Ue. 



and frequently (Total length figured =10 inches.) 



contain a fair . _ _ „ 



proportion of the "^/M 



darker minerals. ^^ \ 



The hornblendic |^ 0, 



rock itself often - 



exhibits much .4 



felspar. Some- 

 times long lenti- .-'•-'"",.."""' 

 cular bands of ^ '''j!.\ .. .-..•.r"?^;-'-'""'"'' 

 the dark rock ' -- ""'"■"•^^T^^•^;^:v^:;^:=^^^•:?:v:v^"!'y^l!!!;^^^ 

 appear ; at others ^ , _ /;; • .::yr'^'^"-^-^^=f:;:^-:^^x:^r 

 it is represented '..>•■ ' " " . '•'^■■'•i^^iVift'^ 

 merely by a few -,-, - .^. ^ ,•-..-...'......- 



broken minerals. 



A very fine section is exposed near the 54 bench-mark. This 

 shows in some places the rock beautifully and wavily banded, the 

 darker parts varying somewhat in their proportions of hornblende 

 and mica, and hence in colour. In places a light-coloured vein 

 cuts across an older banding, and yet seems to form an integral 

 part of the rock ; at others, the bands are disjointed and lie in 

 fragments in the lighter matrix as though broken, while occasionally 

 we find strongly-marked puckers. The granitic rock varies in 

 texture, and sometimes, for a foot or so, is almost free from dark 

 folia. 



Thin sections show the dark rock to consist of a mosaic of green 

 hornblende-crystals, extremely irregular in shape, and plagioclase, 

 the former predominating in quantity. Occasionally, rounded grains 

 of the hornblende are enclosed in the felspar. Apatite is very 

 plentiful, and small zircons are not uncommon. The section also 

 contains a little pleochroic augite with the characteristic colours of 

 hypersthene. The specific gravity of the rock is 2-95. 



The granitic rock, taken at a point where it possesses a minimum 

 of hornblende or mica, is of medium grain and rather pink in colour. 

 A thin section discloses raicrocline in considerable quantity, some 

 orthoclase with micropertbitic intergrowth, and a good deal of 

 plagioclase. Quartz is plentiful. In addition, the rock contains a 

 few irregular flakes of biotite, zircon, and iron-oxide. 



Specimens from the banded part of the same mass are character- 

 ized by rather small hornblendes and micas, often with a few larger 



