DIAMOND IN BRAZIL
The various diamond localities of Brazil do not, however, produce stones of uniform quality; the largest, most beautiful, and those most free from color, have been found at Bagagem. All the stones mined here do not by any means, however, tally with the above description, many are colored brown or black, and besides their undesirable color often exhibit an irregularity of form and numerous other small faults which combine to render them of little value. The stones from the Canavieiras mines stand next in order of quality to those from Bagagem. These, though small, possess a perfect whiteness, few faults, and great regularity of form; by daylight they exhibit a fine luster and play of prismatic colors; by artificial light, however, these qualities are less marked and the stones compare unfavorably with Cape diamonds. Diamantina takes the third place in the quality of the diamonds it produces, and stones from different localities in the district show certain differences among themselves which are well known to the inhabitants; thus sonic mines yield white stones exclusively, others yield only colored stones; the latter, as a rule, predominate; the same applies also to the district of Grao Mogol. Diamonds from the Cincora district rank lowest of all; three-fourths of these are colored, almost all are of irregular forms unfavorable for cutting, and about one-half are fit only to be used as bort. The color of diamonds from Bagagem and Canaviciras is confined to the surface, which is usually bright and only very seldom dull. The surface of stones from Diamantina is not infrequently decidedly rough; it is seldom bright except when the stones have the form of a regularly developed octahedron.
The production of Brazilian diamonds has from the time of their discovery, about 1725, been very considerable. For the eighteenth century and the early decades of the nineteenth century exact official returns were given, but for the years immediately following the first discovery, and also for quite recent years, no absolutely reliable records exist, and the various statements which are met with are based on more or less inaccurate estimates. The official returns account only for stones acquired in a legitimate manner and, of course, leave out of the calculation such as have been surreptitiously mined or obtained by dishonest means. W. L. von Eschwege, at one time chief mining inspector in Brazil, estimated the contraband product to have been at least as large as the legitimate output, while other estimates place it at one-fifth or one-third of this.
The same authority, W. L. von Eschwege, estimated the yearly production between 1730 and 1740 was 20,000 carats, but for the first twenty years he gives the annual production as 144,000 carats, probably in this estimate making an allowance for smuggled stones. According to the official returns, the total production between 1740 and 1772 was 1,666,569 carats, corresponding to an average yearly production of about 52,000 carats, while between 1772 and 1806 the total of 1,030,305 carats, corresponded to a yearly average of about 26,800 carats. For the latter period, 1772 to 1806, F. dos Santos gives the total production as 1,030,305 carats. The production even thus early had therefore considerably fallen off; and was still further diminished during the period between 1730 and 1822, when it stood at 12,000 carats. The total legitimate production of diamonds in Brazil from 1730 to 1822 is estimated by von Eschwege to be 2,983,691 carats. From the first discovery to the year 1850 the total output is given as 10,169,586 carats, or about two tons, and was valued at £15,825,000. Of this, the State of Minas Geraes alone has contributed at least 5,844,000 carats, valued at £9,000,000, that is more than half.
In 1850 and 1851, in consequence of the discovery of the Cincora mines, there was a very heavy production, namely, 300,000 carats per annum, but in 1852 it had sunk to 130,000 carats. From 1851 to 1856 the average yearly yield was 196,200 carats; from 1856 to 1861 it was 184,200 carats; and during the following years remained about the same in amount. In 1858 the leading diamond merchant of the country estimated the average annual output for all previous years at about 90,000 carats, of which 36,000 came from Minas Geraes and 54,000 from Bahia. In 1860 and 1861 the yield appears to have again risen.
Later, Boutan gives the following totals compiled from information derived from various sources: Diamantina from 1843 to 1885 produced 1,500,000 carats. Other localities in Minas Geraes, Goyaz and Matto Grosso, up to 1885 produced 1,500,000 carats. Chapada, in Bahia, from 1840 to 1850 produced 100,000 carats but from 1850 to 1885 it produced 1,500,000 carats. Since diamond-mining ceased to be a Government monopoly, no official records of the production have been kept; the data given above have therefore been compiled from the records of the amounts paid as export duties on diamonds and may be regarded as coming somewhere near the truth, since the number of diamonds exported does not differ from the number mined.
The marked fluctuations in the yearly averages, which will be observed on studying the numbers quoted above, are due to the exhaustion of old deposits and the discovery of new ones. Thus the rise in the yield, which has recently taken place, is due to the discovery of the Canavieiras mines, and it may be reasonably expected that in the future similar new and rich deposits will be discovered, which will have the effect of again raising the total yield. The enormous and steady production of the South African diamond-fields naturally makes the prospector less eager to start in search for new Brazilian deposits. Such, however, may be at any time accidentally discovered, as has, in former times, frequently happened, especially in Bahia.
Rafal Swiecki, geological engineer email contact
This document is in the public domain.