In
India, diamonds are found on a plateau four to six or seven hundred
feet high, in thin alluvial deposits at or near the surface of the
earth. There are two distinct deposits, forming strata in the Upper
Vindyan series of the north, and in the Lower Vindyan section
(Silurian) of the south.
It
is also believed that diamonds exist in the older Paleozoic rocks in
the Himalayas, and it is thought that the diamonds of the Mahanadi
river have been washed down by the headwaters higher up. The diamonds
are always accompanied by pebbles of a siliceous and ferruginous
nature, and a variety of others, among them occasionally, corundum. The
deposits in which they occur are so altered from their original form
that they afford no clue as to the exact nature of the matrix in which
the diamond was crystallized. That the matrix was formed long ages ago,
then disintegrated and scattered over the earth, is about all we know
of the origin of the diamond which was released from its bonds and
strewn over the earth, in India during the ages succeeding.
In
Brazil the sources of the diamond are extensive elevated plateaus the
faces of which are broken up into abrupt, rugged hills and gorges, from
whence the diamonds with their decomposed matrix have been carried
from level to level, as the mountain torrents wore their channels,
through the ages, many being carried by the rivers having their
headwaters in the mountains, down to the plains below. Wherever
diamonds are found they have come evidently from high places, but in
Africa only have they been discovered in their elevation, un-scattered by the waters.
