193 KING: KADAPAH AND KARNUL FORMATIONS. [PART III. 
These are compact, very fine-grained, thin chert-hke beds, of 
which three average specimens of different bands gave the following 
composition :— 
No. 1 No. 2 No. 3 
Loss by ignition... D. 14 03 L3 
Silica 2 2... 9165 83:22 79'65 
Oxides of iron and alumina  ... 11l55 11:25 16:25 
Lime ... We ... trace 83 1:45 
Magnesia doe ی‎ qi ado Soeur m hein E 
Potash ae t 5:22 *04. *24. 
Soda سس‎ cee et 0°53 4:95 581 
100°35 100:59 100-70 
Specimen No. l is a compact, very fine-textured, amygdaloidal, 
porcellanic rock and seems to be an orthoclase felsite. Its composition 
agrees very closely with that of 46 and other felsites of this family 
™ 
given by Dana in his System of Mineralogy (1868). 
No. 2 is a fine grey, compact, chert-hke, porcellanic rock. 
No. 3 is a reddish brown, not so fine-grained, chert-like rock, 
speckled with dark green spots. 
Both these specimens are, according to their composition, oligoclase 
felsites, and answer to analyses of those given by Dana.* 
These silicio-felspathie bands are more like thin beds of chert than 
any other rock; but their peculiarly close association with trap-flows and 
their occasional igneous look, besides their answering in appearance to a 
certain extent to what are called felstone, felsite, or petrosilex by 
petrologists, led at length to the consideration that they could be nothing 
else but felsites. Further examination of these rocks with the blow-pipe 
by Mr. F. R. Mallet of the Geological Survey of India, has also, to a 
great extent, confirmed the supposition of their voleanic origin, while the 
foregoing later analyses of Mr A. Tween are in favor of this view. 
* Dana’s System of Mineralogy,” Fifth Ed. (1868), pp. 347, 351, 358. 
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