iamond is here found in ancient sandstones and
conglomerates, and in the river gravels and sands derived from them.
The sandstones and conglomerates belong to the Vindhyan formation and
overlie the old crystalline rocks: the diamantiferous beds are well
defined, often not more than 1 ft. in thickness, and contain pebbles
of quartzite, jasper, sandstone, slate, &c. The mines fall into five
groups situated on the eastern side of the Deccan plateau about the
following places (beginning from the south), the first three being in
Madras. (1) Chennur near Cuddapah on the river Pennar. (2) Kurnool
near Baneganapalle between the rivers Pennar and Kistna. (3) Kollar
near Bezwada on the river Kistna. (4) Sambalpur on the river Mahanadi
in the Central Provinces. (5) Panna near Allahabad, in Bundelkhand.
The mining has always been carried on by natives of low caste, and by
primitive methods which do not differ much from those described by the
French merchant Jean Baptiste Tavernier (1605-1689), who paid a
prolonged visit to most of the mines between 1638 and 1665 as a
dealer in precious stones. According to his description shallow pits
were sunk, and the gravel excavated was gathered into a walled
enclosure where it was crushed and water was poured over it, and it
was finally sifted in baskets and sorted by hand. The buying and
selling was at that period conducted by young children. In more modern
times there has been the same excavation of shallow pits, and
sluicing, sifting and sorting, by hand labour, the only machinery used
being chain pumps made of earthen bowls to remove the water from the
deeper pits.

At some of the Indian localities spasmodic mining has been carried on
at different periods for centuries, at some the work which had been
long abandoned was revived in recent times, at others it has long been
abandoned altogether. Many of the large stones of antiquity were
probably found in the Kollar group, where Tavernier found 60,000
workers in 1645 (?), the mines having, according to native accounts,
been discovered about 100 years previously. Golconda was the fortress
and the market for the diamond industry at this group of mines, and so
gave its name to them. The old mines have now been completely
abandoned, but in 1891 about 1000 carats were being raised annually in
the neighbourhood of Hyderabad. The Sambalpur group appear to have
been the most anci