Many other minerals are found in this state, but few of them are worked. There are a number of iron outcrops reported which are said to be composed of almost pure ore. Copper has been found in Minas, as well as in several other states, although little exploitation has been done, and platinum is also mined. Brazil contains the largest mines of manganese ore that have yet been discovered. This metal promises to be of more value in the future. Monazite, an essential element in the manufacture of mantles for incandescent gas lights, is mined in large quantities and shipped to Europe.
Many precious stones are found in Brazil. Among them are amethysts, tourmalines, aquamarines, topaz—and, lastly, the diamond. India was the original source of diamonds. In 1728, almost two centuries ago, these precious stones were first discovered in Brazil. For a century and a half Brazil held the absolute supremacy in the production of diamonds, until the discovery of the South African fields transferred the centre of the diamond industry to that region. Although the number of diamonds of Brazil to-day is far less than those of South Africa, it is said by experts that the Brazilian diamonds have a far larger proportion of what are classed as the “first water,” those which have a tinge of bluish steel in them, than any other country, and the diamonds of that country bring the very highest market price.
The centre of the diamond industry in Brazil is at Diamantina, in the state of Minas Geraes, although these precious stones are also found in the states of Motto Grosso, Bahia, Goyaz, and Paraná. Heretofore the methods of mining diamonds in Brazil have been of the very crudest sort, the same that have been used almost from the time of the first discovery. Just recently American capital has purchased the leading mines, and modern dredging machinery has been installed, as well as machinery for the separation of the gravel products from the diamonds. These machines are run by water power generated from the streams along which the diamonds are found. This will revolutionize the diamond industry in Brazil, and the possibilities are that the production of diamonds in that country will be greatly increased.
There is, and has always been, a fascination about the diamond. Not only is it unrivalled for lustre, brilliancy and fire, but it is so hard that no known substance can cut it or make the slightest indentation save, another diamond. The popular saying that it takes a diamond to cut a diamond is literally true. Furthermore, it is composed of pure carbon, and is thus related to two of the commonest of substances, coal and graphite. The appearance of the diamond when first picked up is very different from its appearance after the skillful cutter and polisher have done their work, for it is very dull and the non-expert would probably not recognize it.
The discovery of the diamonds in Brazil was by accident. In searching for gold and silver some singular stones, supposed to be pebbles, were discovered. The negro labourers were attracted by their uncommon qualities and geometric forms, and showed them to their masters. In the card games which were popular in the mining camps these pebbles had been used for counters. At length, an officer, who had been in India, and had seen the diamonds of that country, suspicioned their real nature. Upon a comparison of the weight with other pebbles he found a great difference. As a result some were sent to Lisbon to be examined, from whence they were forwarded to Holland, and the Hollanders pronounced them to be real diamonds. It has been estimated that during the one hundred and eighty-one years since the discovery of diamonds, Brazil has produced two and one-half metric tons of these valuable stones, or twelve million carats. The value of the production each year amounts to about one million dollars of actual value. This is small in comparison with the mines of South Africa, but no such force or vitality has been expended in the mining. And yet the production is much simpler. The diamantiferous fields of South Africa have required the most expensive machinery, and every device that human ingenuity could devise for the successful extraction of the diamonds. In Brazil, so far as discovered, the diamond deposits are all alluvial and are found on the surface, and in or along the beds of rivers. Hence no deep mining is necessary as in Africa. These river gravels also contain a considerable amount of gold, which helps to pay the cost of dredging. The primitive processes in use are very similar to those in use in placer gold washing. The gravel is dug out and placed in small wooden bowls. The miners then proceed to a convenient place on the stream and laboriously wash out their material, gradually getting rid of the particles not wanted. Sometimes a pit is excavated, and a part of the stream diverted into it for the washing process.
Although no diamonds have been found in Brazil as large as some of the extraordinary gems that have been unearthed in the Kimberly mines, some beautiful and large stones have been discovered. One of these, called the “Regent of Portugal,” weighed two hundred and fifteen carats, and has been estimated to be worth more than a million dollars. It is now numbered among the French state jewels. Another was the “Star of the South,” which was found by a negress who was at work in the mines near Diamantina. This diamond weighed in the rough two hundred and fifty-four and one-half carats, but when cut was reduced to one hundred and twenty-five carats. It is a fine stone of first quality. A large one was discovered in 1908 which was one and one-third inches long and three-quarters of an inch in width, which would make it of extraordinary size.
The discovery of the Braganza diamond is an interesting story. This was in 1791. Three men who had been convicted of capital offences were sent out into exile among the Indians and wild beasts. As they were forbidden to enter any city, or hold any communication with the world, they searched for treasure. While washing for gold in the Abaite River, they were attracted by the gleam of a curious stone. As diamond washing was prohibited they took the stone to a priest. He ventured to lead them to the governor, and the diamond was presented to him. At the request of the priest the three men were pardoned, but the government retained the gem.
The black diamonds, called “carbonados,” are found in greater quantities in Brazil than in any other country. These are used solely for commercial purposes in making points for drills. They are as hard as the other diamonds, but lack the transparency and brilliancy of the white stones. The “carbonados” are found in much larger sizes than the others, one of three thousand and seventy-eight carats having been discovered. These stones have a considerable value and are worth from $25 to $75 per carat, the price depending upon the demand and supply. Nothing has ever been discovered that is so good for drilling hard rocks as the diamond drills made from these “carbonados,” and they have been successfully used in drilling many railroad tunnels.