CHAP. 3.] KARNUL FORMATION.—JUMMULMUDGOO GROUP. 75 
seen. The rock is likewise made up, to a large extent, of the same 
mineral as are the lenticular bodies contained in it, thus giving 
even the general surface locally an adamantine lustre. It is so strong 
at times and so like the lustre of corundum that it at first resembles 
a sandstone partly made up of emery, which would have thus given a 
fine rubbing or polishing material ; but subsequent examination showed 
that the mineral is felspar.* 
This lenticular patch of quartzite occurs on the flat and scarped 
terrace above and to the east by north of Taudapurteet ( Bellary District) 
in the neighbourhood of the village of Oorchintala. It occurs apparently 
as a patch on the limestone of the terrace, but on working over the 
adjacent country one soon sees that it is intercalated among the 
limestone by the fact of its being also overlaid by the Nerjee beds. It 
is overlaid by the limestones of the capping of the headland just south 
of the village of Oorchintala, and about a couple of miles north of this 
village there is a low scarp over which the stream falls into a ravine, in 
which those quartzites are overlying the thin-bedded grey limestones 
which come under the blue beds. 
The thickest part of these intercalated quartzites cannot now 
40 feet of intercalated PE more than 40 feet ; and they occupy an area of 
Quare some seven or eight square miles. 
It 1s unfortunate that these die out to the north, for they thus cannot 
be connected with those thin bands of quartzite occurring at the western 
bases of the Banaganpilly hills; but they certainly seem all to belong to 
one period of deposition, for they occupy as nearly as possible the 
same horizon among the limestones. The felspathic characters are not . 
observable among these beds to the north-west of Banaganpilly. 
* On examination with a magnifier, the lenticular assemblages of matter are found 
to be made up of coarse rounded grains of white quartz in a glassy crystalline matrix of 
felspar. 
T On the right bank of the Penn-air ; north-east corner of sheet 59 of the Indian Atlas. 
ve) 
