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The ancient source of the world's supply of diamonds was exclusively India; later Borneo produced some, but up to about the year 1700 India was the sole source, and from the anciently famous diamond district and market of Golconda, between Bombay and Madras, in the southern portion, came the Kohinoor, the blue Hope Diamond, and other world-famous gems. The French traveller Tavernier recorded that he visited Golconda in 1665 and that sixty thousand men were employed there; this field is now abandoned. The modern diamond mines of India are in three principal localities. The Madras Presidency in Southern India, which includes the districts of Kadapah, Bellary, Karnul, Kistna, and Godavari, and also ancient Golconda. The second locality is farther north between the Mahanadi and Godavari rivers, and includes Sambalpur and Waigarh eighty miles south-east of Nagpur, as well as portions of Chutia Nagpur province. Bundelkhand, Central India, contains the third region, the principal field being near the city of Panna. The product of all the mines of India has decreased until now it is but a small part of the world's supply.
Borneo's fields produce annually about three thousand carats. The basin of the Kapoeas River, on the western slope of the Ratoos Mountain, near the town of Pontianak, is the principal locality.
In 1728 diamonds were discovered in Brazil. They were found by gold miners in river sands, but the finders did not identify the curious crystals sometimes found in their pans when washing the sand for gold-dust and scales. It is related that a monk who had seen diamonds mined in India recognised the characteristics of the Brazilian stones. No sooner had the news of the valuable discovery reached the Portuguese than the King of Portugal seized for the Crown the lands known or thought likely to be diamondiferous. Near Diamantina, in Minas Geraes, the diamonds are obtained from both river and prairie washings. The river deposits are rolled quartz pebbles, mixed with or united by a ferruginous clay of which the usual foundation is talcose clays. Associated minerals include, rutile, hematite, ilmenite, quartz, kyanite, tourmaline, gold, garnet, and zircon. The finest stones result from the prairie washings, where the diamonds occur in a conglomerate of quartz fragments overlaid by earth or sand. Bagagem is a productive locality, and there a fine stone weighing 247 1/2 carats was found. Abatehe, Minas Geraes, is another important field. Diamonds are also found at Lencaes, Bahia; along the river Cacholira, chiefly at Surua and Sinorca, and on the Salobro and other branches of the Pardo River. |
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Precious Stones Guide Vol 4
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