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Ch. 6: The Diamond

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PRECIOUS STONES.
113
varieties of Chalcedony, include Garnet, Beryl, and Topaz.
Other deposits in river gravel occur about 200 miles south-west of the previous group at Wairagarh ; also 100 miles north-east to 200 miles north-north-east of the Mahanadi deposits, near Jushpur, and about Sumelpur. Many of these seem to have been of considerable importance at the time Tavernier visited them (1560), but now they are not of great interest as productive deposits.
A large group of deposits extends south-west from Allahabad for 150 miles or so, and is known as the Panna group. At none of these Panna mines is the mineral actually found in the rock in which it was developed. In some of the workings it occurs in thin beds of detrital rocks of great age; in others, again, simply in sands and gravels derived from a further disintegration of these detrital rocks. Only at Birjpur has the material been cemented into a firm conglomerate. The associated minerals do not seem to be of special interest, consisting only of siliceous minerals in most cases.
In the early part of the eighteenth century Diamonds were found in Brazil in the gold washings in the State of Minas Geraes, though not definitely recognised as such until they came into the hands of the Dutch consul at Lisbon. They are usually said to have been found first a short distance to the west of Tejuco, a town which afterwards became known as Diamantina, lying some 340 miles north of Rio de Janeiro. The mineral is found under different conditions in the various kinds of workings, but the most important from the point of view of the origin of the mineral are what are known as " plateau workings.2' These occur on the high p.s.                                                                                   i
Ch. 6: The Diamond Page of 311 Ch. 6: The Diamond
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