ent mines of all, but they were not worked later
than 1850. The Panna group were the most productive during the 19th
century. India was no doubt the source of all the large stones of
antiquity; a stone of 67-3/8 carats was found at Wajra Karur in the
Chennur group in 1881, and one of 210-1/2 carats at Hira Khund in 1809.
Other Indian localities besides those mentioned above are Simla, in
the N.W. Provinces, where a few stones have been found, and a district
on the Gouel and the Sunk rivers in Bengal, which V. Ball has
identified with the Soumelpour mentioned by Tavernier. The mines of
Golconda and Kurnool were described as early as 1677 in the twelfth
volume of the _Philosophical Transactions_ of the Royal Society. At
the present time very few Indian diamonds find their way out of the
country, and, so far as the world's supply is concerned, Indian mining
of diamonds may be considered extinct. The first blow to this industry
was the discovery of the Brazilian mines in Minas Geraes and Bahia.

_Brazil._---Diamonds were found about 1725 at Tejuco (now Diamantina)
in Minas Geraes, and the mining became important about 1740. The chief
districts in Minas Geraes are (1) Bagagem on the W. side of the Serra
da Mata da Corda; (2) Rio Abaete on the E. side of the same range;
these two districts being among the head waters of the Rio de San
Francisco and its tributaries; (3) Diamantina, on and about the
watershed separating the Rio de San Francisco from the Rio
Jequitinhonha; and (4) Grao Mogul, nearly 200 m. to the N.E. of
Diamantina on the latter river.

The Rio Abaete district was worked on a considerable scale between
1785 and 1807, but is now abandoned. Diamantina is at present the most
important district; it occupies a mountainous plateau, and the
diamonds are found both on the plateau and in the river valleys below
it. The mountains consist here of an ancient laminated micaceous
quartzite, which is in parts a flexible sandstone known as
itacolumite, and in parts a conglomerate; it is interbedded with
clay-slate, mica-schist, hornblende-schist and haematite-schist, and
intersected by veins of quartz. This series is overlain unconformably
by a younger quartzite of similar character, and itself rests upon the
crystalline schists. The diamond is found under three conditions: (1)
in the gravels of the present rivers, embedded in a ferruginous
clay-cemented c