100 KING: KADAPAH AND KARNÜL FORMATIONS. [PART II. 
The dip of the underlying shales, traps, &c., is really so low on the 
northern face of the hill that it is not surprising that previous observers 
have been led into the error of supposing that the quartzites overlaid 
these rocks conformably ; but had time been allowed them, they would 
doubtless eventually have made out that this was not the case. 
The quartzite covering is from 20 to 30 feet in thickness; and 
it is pierced here and there over the Banaganpilly end of the hill by 
shafts of 15 feet or less, from the bottoms of which nearly horizontal 
galleries are run to get at the seams of diamond gangue. The capping is 
composed of compact grits and sandstones im thickish beds above and 
somewhat thinner bedded towards the bottom. Externally the rocks are 
hard and vitreous. At the level of the galleries there are beds of coarse 
pebbly conglomerate, occasionally a breccia, which are sandy and clayey, 
and with these run seams of more shaly and clayey stuff. There is no 
trace of the clayey constitution on the outside along the outerop ; nor are 
there any distinct bands of shales; there are only some sandy shales 
down at or near the bottom of the series. On the other hand, down in 
the shafts, owing largely to the confined moisture (never to be expected 
from the atmospheric conditions of the country), heat, and other 
decomposing influences, the rocks are as unaltered-looking sandstone, 
grits, clayey varieties of these, and coarse shales as it is possible to meet. 
It is in these more or less clayey and shaly seams of pebbly beds that 
the diamonds are found. 
In the mines the coolies were picking out a seam of about six or 
eight inches in thickness, occurring with thicker and harder beds of 
sandstone, and which they said was the diamond layer; this rock when 
brought to light turned out to be an easily-broken-up damp clayey 
conglomerate and partly breccia, of small rounded fragments and pebbles 
of black, red, green, and pale-colored shales and cherts, and of quartzite 
with large and small grains of dirty and pellucid quartz. This was 
the rock extracted in all the mimes then being worked. . 
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