advances in this direction of late years, that we must look for the true explanation.
But
the absence of any clear evidence on the subject may be due to the fact
that it is still a matter of doubt whether, in any single recorded case
in India, a diamond has been found in its original matrix. The lowest
diamond-bearing stratum, at the base of the Karnul series, is itself a
detrital conglomerate, and it is not unreasonable to suppose that the
diamonds may, like the other ingredients, have been derived from some
older metamorphosed rocks.
Mr.
King* discusses some apparent cases of mines in the Kadapah series of
rocks which underlie the Karnuls, but he says there is ''still a doubt
as to whether true rock-workings in these beds were ever successful."
Elsewhere, I.e., p. 101, however, he states of the diamonds shown to him at Banaganpilly that—
Nearly
all the specimens were more or less perfect modifications of the
octahedron, with curved facets; one of them had each of its facets
crowned with a little pyramid of tables.f
They
were smooth, tolerably bright and shining, and did not look as if they
had been worn; in fact, they seemed to me to have been crystals in situ in the rock. In colour they were pale blue, or green and yellow.
Captain
Newbold, in discussing this subject, without much difficulty disposes
of Captain Franklin's suggestion that the beds containing the diamonds
of
* "Memoirs of the Geological Survey of India," vol. viii. p. 88.
t Newbold speaks of the diamonds shown to him at the same locality as being "but imperfectly crystallized."— J. R.A. S. vol. vii.
