Amazing articles on just about every subject...


Diamonds Mines Of Brazil

( Originally Published 1911 )



DIAMONDS were first discovered in Brazil by natives while washing the sands for gold, in the early part of the eighteenth century. The year 1725 is given as the date, but they were not recognized until 1727 and may have been found even earlier. There is a tradition that the stones afterwards found to be diamonds, were known in the gold washings as early as 1670. Inasmuch as the streams in which the gold washings were conducted proved later to be very rich in diamonds, it is quite probable that they had attracted attention for many years before their value was known. It is said that the gold miners used them as counters in their games of chance, and that a man who had seen rough diamonds in India, observing them in the hands of the miners and noting the similarity, secured a number of them and took them to Lisbon the following year, where their identity was established. He sold them, and in doing so drew attention to the new fields.

The discovery was made in the neighborhood of Tejuco, a town in the district of Serra do Frio, province of Minas Geraes, about 300 miles north of Rio de Janeiro and about 250 miles west of the Atlantic coast. Tejuco is now called Diamantina and is the center of the diamond industry of the Minas Geraes district. The district is an exceedingly rough plateau at an elevation of about 4,000 feet above sea level, cut up by gorges and deep valleys, enclosed by abrupt, mountainous walls. Throughout, numerous streams rise, joining later to form tributaries of the Jequetinhonha flowing to the north and east, of the Sao Francisco going north, and of the Doce, running south and east. The mountains divide the drainage of the Sao Francisco on the west, and the Jequetinhonha and Doce on the east. The Diamantina district lies between the Rio das Valhas on the west, and the headwaters of the Jequetinhonha and Doce on the east.

When it became known that diamonds were to be picked up thereabouts, people flocked to the neighborhood and found them in all directions, in and near the streams. A few were found also between the headwaters of two tributaries of the Rio Doce, about half way between Diamantina and Rio de Janeiro, near the town of Cocaes.

Brazil was at this time a Portuguese dependency, and when the home government learned that diamonds were being found in the colony, it laid claim to all diamond-bearing lands and streams, but in the beginning gave permission to anyone to mine on payment of toll for each slave employed, the number of them being pre-scribed by contract. This tax was constantly raised until it became so onerous that nobody would mine under the conditions. But the diamondiferous gravels lay scattered in every direction, and the hills held also many natives and escaped slaves who were expert miners. These smugglers, or " Garimpeiros " as they were called, undoubtedly continued to wash the sands surreptitiously for diamonds, adding many to the world's stock of precious stones which have never been entered up on statistic's ledgers.

To revive the industry, the government in 1740 granted concessions, and the fields were worked in that way, but with poor results for the government, until 1772, when the authorities decided to work the mines for government account, and did so until Brazil threw off the Portuguese yoke in 1834. During that period all the best stones found were sent to the Crown jewels at Lisbon. The others were sold to dealers and shipped from Rio and Bahia city to Europe.

After Brazil established her own government, mining privileges could be had anywhere by anyone on payment of a small tax to the government, and a proprietary tax of 25 per cent. on the gross receipts. In addition / per cent. was charged on exports. Although the laws have been modified at various times, this general plan has been adhered to from that time until now.

In those early days, and until the prejudice excited by the dealers in Indian diamonds against the Brazilian had been overcome, the diamonds were shipped first to Goa, a Portuguese possession in India, and then sent from there as Indian stones. The Hollanders used the prejudice existing against Brazilian diamonds, in an effort to get control of the entire output, but they failed to gain it, and most of the diamonds were sent to Lon-don. Later, many of them went to Paris also.

The early method of working the fields was about the same as now except that slave labor was employed. Gangs of slaves gathered and washed the cascalho under the eye of an overseer who sat among them on a shaded elevation, armed with a long-lashed whip. When one found a diamond, he gave a signal to the overseer, who took it from him and deposited it in a bowl of water at his side. At the end of the day's labor the stones were counted, weighed, recorded, and deposited in a safe place. Many of the slaves were adept thieves. Some were so expert and had so many tricks of concealment, that the most suspicious watchfulness failed to detect them, and the stones they concealed were undoubtedly of the best. If discovered they were punished unmercifully. As an offset to the barbarous inflictions for dishonesty, a system of rewards for honesty was established. Small presents of cotton cloth, tobacco and the like, were distributed to the successful, and while slaves were cheap, the finder of a stone weighing one oitava (17% carats) or over, received his freedom. Nevertheless diamonds were stolen constantly and many slaves escaped to the interior, thereby extending the fields, for many of the diamondiferous deposits were discovered by garimpeiros, who could prospect only where the hand of the government did not reach.

In 1785, garimpeiros discovered diamonds about one hundred miles west of Diamantina between the streams which form the head waters of the Sao Francisco running north and the tributaries of the Paranahiba flowing south, This district is also in the province of Minas Geraes, though the western part of it is very close to the borders of Goyaz. Bagagem is to these fields what Tejuco or Diamantina was to its district. For some time the garimpeiros worked these fields with, out concessions, and unhampered by the authorities. The district became prominent because several large stones were found in it. The first discoveries were on the eastern side, one of the largest of all Brazilian diamonds being found in the Rio Abaété. Later, as the miners extended their operations westward, large stones were found there also, the " Star of the South " being discovered near Bagagem.

In 1827 diamonds were found in the neighborhood of Grao Mogol, about 150 miles north and a little east of Diamantina. The neighborhood had been prospected some fourteen or fifteen years earlier. The diamondiferous deposits lie about several tributaries of the Jequetinhonha having their rise in a chain of hills which follow the river on the northwest side. The crystals are found there in a solid sandstone conglomerate which the miners named " Pigeons' Eggs." As with all new fields, a great many gathered at these diggings, so that in 1839 it was estimated there were 2,000 persons working in the district. The number soon after dwindled rapidly and has since become unimportant.

In January, 1867, a garimpeiro found a diamond in the gorgulho near the Agua Suja brook, about 12 miles south of Bagagem, and a rush in that direction ensued. A majority of the claims were worked on a percentage. The garimpeiros rented parts of claims and hired slave labor. Bullock skins were used to carry the dirt down from the gorgulho to stream level. For a time they made money fast. Then carne the African discoveries and prices broke. Buyers refused to pay as much as they had been paying, and the miners, suspicious of them, refused to sell at lower figures. They borrowed money to carry their expenses and held their diamonds, until eventually most of them lost all they had.

The discoveries of diamonds in Minas Geraes naturally excited interest throughout Brazil, and the tales of fortunes picked out of the sands of the hills and rivers, caused the natives everywhere to look for them. They were found in and about the streams near the western borders of Minas Geraes in the province of Goyaz. Up to 185o it is said that 252,000 carats were taken from the Paranahiba, the Rio Claro and tributary streams.

Many streams in Matto Grosso, up to the Bolivian frontier proved to be diamondiferous. The source of the Paraguay river and its tributaries near Diamantina, particularly the right side of Rio Cuyaba, yielded many diamonds. They were all small stones and very many were colored, but some were very good. Unlike most of the Brazilian diamonds, the crystals were distinguished by very brilliant exteriors. Considerably over one mil-lion carats were reported from this district by 1850.

In the province of S. Paolo, south of Minas Geraes, diamonds were taken from the Rio Parana and its tributaries, and some were found in the Rio Tibagy and its tributaries the Yapo and the Pitangru, in the province of Parana. They were also found in deposits on the neighboring heights. The stones were found chiefly in a Devonian sandstone through which the streams run. The crystals were small, and the quantity found too meager to encourage persistent work, so that regular mining was given up.

Equally important with the fields of Minas Geraes are those of Bahia. Though divided into a number of districts there are two natural divisions only, viz.: the section about the Paraguassu river and its tributaries and the tributaries of the Rio Sao Francisco, and another and smaller area along the valley of the Pardo river near the coast south and east of the Paraguassu fields. This is called the Cannavieiras district, from the port of that name by which entry to it is made. At present the diamond-mining industry is practically confined to the States of Minas Geraes and Bahia, the fields of the latter being more important because carbon is found in them with the diamonds.

It is said that diamonds were known to exist in the State of Bahia as far back as 1755, but the government, thinking that mining would be hurtful to the agricultural interests, refused to allow any mining to be done. The date of the discovery of diamonds in Bahia is therefore given usually as 1821, when they were found in the Serra do Sincorá, but in common with many other discoveries it was not followed immediately by the development of an industry. To find an occasional diamond in a wide territory of wild country difficult of access, may indicate that it contains great treasures, but the hiding places are usually discovered by accident long after the fact of their existence is known. It was so in this instance. In 1844, 23 years after the discovery, Jose Persira do Prado, journeying to Bahia city, camped on the bank of the Mocuge, a small tributary of the Paraguassu river, and quite accidentally found a quantity. This becoming known, many went there. S. Joao do Paraguassu, or Santa Isabel, was founded on the site of the discovery, and has remained a center of the district, which from that time grew in area and importance.

The State divides the Bahia diamond region into 14 districts : Lencoes, Andarahy, Chique-Chique, Santa Isabel, Cravada, Lavinha, Campestre, Morro do Chapeo, Born Jesus, S. Ignacio, Chapeda Velha, Paraguassu, Sincorá and Cannavieiras, all but the latter being on the Paraguassu river and its tributaries and the tributaries of the Rio Sao Francisco. Not only are the Paraguassu fields much more extensive, but they are also more productive. The diamonds from that section are also finer, but not as perfect usually as those of the Cannavieiras district. The most productive part of the Paraguassu fields is about four days journey from Bahia city. The route is by small steamer across the bay and up the Paraguassu river about 45 miles to Cachoeira, a journey of six to eight hours, then by train next day 155 miles to Bandeira de Mello, consuming ten to twelve hours, from which point there is a two days' journey of 64 miles by mule to Andarahy.

Another way to the Bahia fields, is to go by the Bahia and Sao Francisco Railway north to Queimadas or Villa Nova, and from either of those points to the interior by mule-back, or to continue on to Joazeiro by rail and then by boat up the Sao Francisco, going south from there by mule-back. This route taps the diamondiferous district lying between Rio Jacaré and Rio do Salitre, or at Chique-Chique brings one near to the fields extending south to the mountain between the Rio Paramirim on the west and the Lencoes district on the east. The Bandeira de Mello route reaches the fields which extend from Morro do Chapeo in the north through Lencoes and Mocuge to Sincorá in the south.

Diamonds are found at Joao Amaro, 103 miles from Cachoeira, in the bed of the river, but very few are found between there and Andarahy. The Paraguassu fields extend from the village of Sincorá in the south to the Serra do Tombador in the north, and from east of Morro do Chapeo to Chique-Chique and the Rio Paramirim in the west. The most productive district so far lies between Sincorá in the south and about 25 miles beyond the village of Morro do Chapeo in the north. There may be other districts as rich, but this has a reliable water supply and has therefore been very thoroughly explored. In some sections the streams are dry in the dry seasons and short-lived torrents in the wet seasons, making it difficult to gather the cascalho in the one and to wash it in the other. The fields here also are very compact, extending about 150 miles north and south with an east to west width of about 15 to 30 miles. All the Bahia fields of this section lie within a strip of country about 225 miles north and south by 140 miles east and west. Diamonds are found, however, in the rivers having their rise in the diamond hills, far beyond the diamondiferous region. In 1898 diamonds were found with gold in the Rio Itapicuri, 250 miles below the town of Queimadas.

The diamonds are sold to buyers on the fields. These men assort the stones into five grades. " Bons " are crystals of good shape and color; " fazenda fina " are small and tinted, but fine; "melee " are imperfect and off color; " vitrie " or vidrilhos are very small bright stones of various colors; "fundos" are broken or defective crystals mixed with second quality carbons. The stones are usually small. Of a thousand carats taken as they were found several years ago, the largest stone weighed 3 1/2 carats. That would produce a cut diamond of less than 1% carats. About thirty per cent. of the production are fundos. It was reported in 1903 that prices paid at the fields averaged, $11.50 for No. 1; $10.50 for No. 2; $5.00 for No 3 and $2.50 for No. 5, per carat. They are sold by the oitava (17 1/2 carats). Vitrie are sold by the grao (about 1/4 carat), in which there are six or eight stones. They brought about $2.88 at the time.

According to former Vice-counsel Rowe, the limit of price paid by the field buyers of Bahia in the spring of 1906 was as follows:

Bons, good, well formed stones averaging 1/2 carat 860 milreis per oitava = $16.38 per et.
Bons, 6 to 8 graos each .... 20 milreis per grao = 27.38 per ct.
Bons, 4 graos each 16 milreis per grao = 21.90 per ct.
Bons, 10 to 16 graos each.. 25 milreis per grao = 34.25 per ct.
Fazenda fina 396 milreis per oitava = 7.55 per ct.
Vitrie 7 milreis per grao = 9.58 per ct.
Fundos 108 milreis per oitava = 2.06 per ct.

The current rate of exchange at that time being at 17 pence to the milreis, the latter is reckoned in the above figures at 3 to the dollar. There are 72 graos to the oitava which equals 17 1/2 carats; a grao is therefore about 1/4 carat. Nearly all the stones are exported uncut, though there are several cutting establishments in the diamond region and one in Bahia city. To get a fair idea of the value of the stones in the market, there should be added the cost of transportation to Bahia, the export duty equaling about 13 per cent., dealer's profit, and steamer and insurance charges. When this is done it will be found that the Brazilian fields have approximated their prices closely to those established by the Diamond Syndicate in London.

Mining is conducted in a general way, the same as in all other alluvial deposits the world over, though no effort is made to divert the streams, as is done in some cases in the Minas Geraes diggings. A method peculiar to the Paraguassu, is employed largely on the main river, especially from Joao Amaro to Andarahy. The miners use diving machines, probably movable caissons, in which a man can work for several hours on the river bottom. Under cover of one of these, two men work alternately it is said, in three-hour shifts, gathering the cascalho into sacks lowered to them from the surface. Others dive for the cascalho much the same as the pearl divers dive on the pearl banks, gathering as much of the gravel as they can during the submergence. In the shallows, others drag the gravel into the mouths of sacks with their feet. The diamondiferous material is found not only in the beds of the streams and rivers, but also in fissures and gullies in the rocks which bank the valleys of the water-courses, as in the other Brazilian fields. The sands and gravels are gathered from the beds of the streams in dry seasons, and from fissures and beds in the rocks during the wet seasons. The richest finds are made usually in pot-holes in the river beds.

The tools and methods used in the mining are crude, and some think that with capital and machinery, better results could be obtained, but it is doubtful if it would be as profitable on the average. Undoubtedly there are great deposits of diamondiferous material yet unworked, and there are doubtless rich gravels in the sections al-ready worked, which cannot be reached with the appliances now in use, as for instance the lower parts of the deposits in gullies and fissures in the rocks, river bottoms which have been covered by débris from washings on the streams Above, and the like, but with deposits of uncertain richness, which may be here or may be there over square miles of very rough country, the odds seem to be largely against adequate returns for an expensive equipment. In the Minas Geraes district, two modern gold dredges adapted to save diamonds have been lately installed on the Jequetinhonha by American companies. The mining laws are another difficulty. Though liberal on the face, there are uncertainties which have proved costly. A former leaseholder may establish a claim, through some irregularity in a previous transfer, after the leasehold has been developed at great expense by a stranger ignorant of prior conditions. It should be remembered that the various States in which diamonds occur make their own laws governing the mining for them, and as they are somewhat complicated, an attempt to state the provisions definitely might prove misleading. As written, they tend to encourage enterprises of that character. Concessions are to be had on apparently easy terms. Persons of any nationality can take out a claim, but the authorities pass on the ability of the applicants to prosecute the work. In a general way, mining lands belong to the State. If diamonds are discovered on private property, the discoverer can be empowered by the State to prospect and mine, by securing the owner against surface damage to the property and paying a tax to the government. If the discovery it made on government lands, he can obtain a concession or a license to dig within certain prescribed limits, and if in the bed of a river, within a certain length of it, by making application to the authorities, and paying a small tax. In the case of a concession he must also prove his financial ability to be adequate to the undertaking. A prescribed time is allowed in which to commence operations and make them commensurate with the concession, at the expiration of which, if satisfactory work has not been done, the claim may be reentered by another.

Altogether, the laws and conditions favor individual digging under a mining license. The concessioners and leaseholders usually find it to be more safe and profitable to allow miners to mine on their concessions for a royalty of from one-fifth to one-quarter of the value of the diamonds and carbon found, than to attempt to mine on their own account with hired labor. As the miners sell the diamonds to the field buyers of the cities, and the latter arrange to inform the leaseholders of the amount handled, and in some cases to reserve his royalty, the owner of the concession gets in that way more than would escape the thievery of hired labor to him, and with less trouble.

The field-buyers of Bahia, who represent a number of exporters in Bahia city, work independently, and the miners get the equivalent of outside market rates less costs and a fair profit for transference from the fields. The miners usually store the cascalho and wash it week ends. They are very expert in picking diamonds and carbon from similar stones.

The world's supply of carbonado, or " carbons " as the stones are called, comes from the Bahia fields. They are found with the diamonds in the Paraguassu diggings, and were first discovered in 1843 in grupiaras at San Jose, district Sincorá. Prior to 1856 they were thought to be valueless and were thrown away. It is said that there are swamps in the diamond fields, beneath which the diamondiferous deposits disappear. These deposits have been worked to the edge of the morass and then abandoned for lack of machinery to drain, and it is thought that in addition to the deposits lying under them, the swamps contain large quantities of carbonado that have been washed into them with the tailings and lost during the years when the value of carbons was unknown.

The output was said to average about 2,500 carats per month in 1902, but must be very much larger now and probably was at that time also. There is a steady and increasing demand for carbons owing to the constant increase of drilling, pumping, and other machinery requiring a very hard substance. The average weight of the stones found is about six carats. The most desirable sizes are those weighing from one to six carats, those being the sizes used generally for higher mechanical purposes. Larger stones are broken up and the pieces have the advantage over the natural stones that they show the inner quality of the stone. Nevertheless, selected natural stones are preferred by expert engineers, because the natural formation renders them less liable to wear and breakage than the square corners and sharp edges of the broken up stones. Some enormous pieces have been found. The first very large one, discovered on the ledge of a mountain in the Lencoes district in 1895 weighed 3,078 carats. It measured about 3 inches x 3 inches x 3% inches. I. K. Gulland of London bought it September 15, 1895, of Kahn & Co. of Bahia for Ł6,400. He broke it up into pieces suitable for diamond drills and sold it for ten per cent. profit. Seven years later it would have brought four times as much. A piece of 975 carats was found the year previous. It was broken up in Paris and sold for a sum equal to over $19,000. The Parisian dealer was not fortunate, as it cost him more. Another large piece found in 1901, of fine quality and weighing 750 carats, was broken to pieces of three to four carats. Another large carbon weighing 650 3/64 carats was found in 1909, and at present is not broken up. It is of good quality and worth in New York about $55 per carat. The specific gravity of good carbons ranges from 3.15 to 3.30. If a carbon is lower than 3.15 it is not sufficiently crystalline; if over 3.30, it is over crystallized for good work, approaching bort in construction. This piece has a specific gravity of 3.22.

The Cannavieiras district is quite distinct geographic-ally from the other Bahia districts, which are all, though divided into districts surrounding as many towns as centers, practically the same fields. This came to be known as a diamond district about 1881. It is reached by the Pardo river in canoes 56 miles to Jacaranda, and from there by mule-back, 12 miles higher up the river to Salobro. The early workings were confined to the river and the immediate neighborhood, and the country has not been as widely prospected as in other fields, owing to a lack of water in many directions. The diamonds are usually small and clear, but do not average as good in quality as those of the Paraguassu districts. Little or no carbon is found.

There are two ways of reaching Diamantina, the center of the principal Minas Geraes diamond fields. First, by leaving the railway at Curvelho and making the journey of three or four days by mule-train through a very rough country by a trail which passes over two rivers separated by high ridges. Where the trail crosses the main ridge, which is 5,000 feet high, it can be done only on mule- or horse-back. The other way is by continuing north by rail to Curalinho and on from there by rough stages and wagons. Though the latter way does not contain as many blood-curdling passes as the other, it was considered worse, formerly, being very fatiguing. The introduction of rough country wagons of American make, over this route, ameliorated the conditions, and they have been further improved by a betterment of the road. Diamantina can now be reached by fast mule-back over this route in two days from the railroad.

This field extends over an immense territory of a very wild, rough character, on both sides of the northern end of the Serra do Espinhaco. It is a plateau broken up by steep-sided, deep valleys, in which numerous streams that feed the Jequetinhonha and the Sao Francisco rivers, have their rise. The Jequetinhonha after running north-east, when it turns due east to empty into the Atlantic, becomes the Rio Belmonte. The diamonds are found in the streams, the valleys of the streams, and in crevices and depressions in the hills.

Operations in Brazil are carried on now largely by " servicoes,"— bands of workmen hired by one man or organized into squads which divide results. These select " journaleiro," or spots where they feel sure of finding diamonds, and proceed to gather the cascalho and wash it in their primitive way according to the season and conditions. The natives carry small wooden bottles, made by boring out the center of a straight twig into which they fit a wooden stopper, for the purpose of depositing the small diamonds as they find them in the wash. Rich finds are sometimes made in a " poco " or pool in the river bed in which the cascalho has been caught, especially where a " cochoeira " or waterfall has been for ages washing rich deposits from above. The conical wooden dish used for washing is called " bateia." The " carimbé " is a smaller wooden bowl in which the cascalho is carried on the head. The river beds are worked in the dry season, and the deposits in fissures or depressions in the rocks, in wet seasons. Carbons do not occur in Minas Geraes, but larger diamonds are found than in Bahia.

The Agua Suja district is a southern continuation of these fields. It lies on the Bagagem river, one of the tributaries of the Paranhiba, 12 miles south and a little east of Bagagem, about three thousand feet above sea level. The Mogyana Railroad runs to Uberaba, 67 miles from Bagagem. The region is a series of terraces sloping to the west from Serra da Canastea to the Rio Grande. The fall of the rivers is considerable, and the currents therefore are swift. The Rio das Velhas narrows near Agua Suja to 50 feet, and rushes over two falls of ten and thirteen feet with great velocity. The Rio Claro, a tributary of the Rio das Velhas, also runs very swiftly over a bed of horizontal gravels and limonite conglomerate. The Bagagem river has a drop of 1/2 percent. between Bagagem and Agua Suja. L. B. Gonzaga de Campos describes the bottom of the valley of the Bagagem river as consisting of mica-schist, and the soil on the slope towards Agua Suja as alluvial with pebbles of limonite. The Agua Suja valley, which runs east and west, and that of the Bagagem river one and a half miles to the west, are full of old excavations of diamond workers. The soil near Agua Suja church is alluvial with patches of ferruginous gravel. The basal strata are of mica-schist and contain quartz, muscovite, altered tourmalines and almandine garnets. The heaviest pan-residues from this rock are magnetite, ilmenite, rutile, tourmaline, staurolite, and zircon. Large deposits are found in hollows in the hills. An examination of the rear wall of an excavation in one of these deposits, which illustrates their general character in this neighborhood is given by L. F. Gonzaga de Campos, as follows :

Ft. In.

Ferruginous clay and gorgulho 4 3
Ferruginous clay 13 2
Hard Clay schist (Secundina) 4
Estrellada (diamondiferous) 2
Secundina (diamondiferous) 3 3
Tauâ (diamondiferous) 13 2

The ferruginous clay, like the " red earth" of S. Paulo and the wet diggings of Africa, leaves a residue on washing of ilmenite, magnetite, apatite, an abundance of hydrated oxides of iron, and water-worn quartz pebbles. The gorgulho contains fragments of quartz crystals, brown iron, hydroxide pebbles, needle-emerald (tourmaline) and fragments 0f rutile. Usually this carries few diamonds, but larger ones than the more prolific upper parts of the deposits. The "Star of the South" was found in a ferruginous clay above the gorgulho. The clay-schist " secundina " usually over-lays the diamondiferous beds. It is rather soft and plastic but not easily disintegrated. Diamonds are usually found in any locality where "estrellada " occurs. Between its various colors are white points containing fragments of quartz. These give it the starry effect for which it is named. It consists of decomposed stratified rocks reduced to a clay. Among its components are, hornfels, fragments of opal, and pebbles of augite-porphyry. The diamonds found in it are usually small and have an appearance like bort, but cut to very brilliant stones.

Tauá is similar to estrellada, but is composed of larger fragments and the white spots are absent. Between alternate plates of red or green amphibolites and decomposed gray and yellow mica-schist, are pebbles of augiteporphyry and fragments of opaline chalcedony. In the red or yellow containing iron oxide and fragments of quartz, which fills the spaces between the pebbles, the diamonds are found. Tauá is the chief diamondiferous deposit of the Agua Suja district inasmuch as it is usually greater in depth and carries more diamonds, though the gorgulho yields larger stones. Being above water level it can be worked more economically also.

On both sides of the Bagagem river are shallow beds of gravel consisting largely of fragments of amphibolites, quartz and hyalo-tourmalines called " grupiaras." These are diamondiferous but have been about exhausted. The river beds are undoubtedly diamondiferous but their value cannot be fully determined without machinery capable of dredging the bottoms. The deep pools and depressions into which probably the richest washings of the torrents have been carried, are beyond the reach of the methods and appliances at present in vogue throughout the Brazilian fields. For more than a century the gravels of the hills and river valleys and accessible places in the river bottoms of the Minas Geraes diamond fields have been worked for diamonds, but there yet remains in the unworked portions of the streams themselves, the greatest likelihood of the richest deposits of all.

Scientists have thought that the matrix of the diamond in Brazil is itacolumite, a kind of laminated granular quartz or ferruginous quartzose, and some have claimed that the sandstone of the Grao Mogol district in which diamonds have been found, was the matrix. The diamonds are found under similar conditions, and in general, with certain companion minerals, throughout the Brazilian fields, in what might be termed three tiers of placement : in the heights : above the present water levels, and below the water levels in the beds of the streams. In the heights, where they are found in the itacolumite, the stones are not as plentiful, but they average larger in size, and the edges of the crystals are not as water-worn as those taken from the lower levels. On the hill-sides of the river valleys they are more numerous, more water-worn, and some of the heavier companion minerals are not as plentiful. The sands and gravels of the rivers yield even more diamonds, but they are usually smaller, and are worn smoother. The minerals accompanying them are of the lighter varieties. From these facts it is assumed that in the ancient upheaval, the diamondiferous material was exuded through fissures in the basic rocks, from which the rains of ages washed the lighter pebbles to lower levels. From these deposits the smaller stones were again rolled lower as the water-courses cut deeper into the valleys, to the river beds of the present, each process being marked by the increased rounding of the crystal edges and the diminution in size and weight of the pebbles carried along from stage to stage.

Although there is a general resemblance between the material of the several districts of Brazil in which diamonds are found; it is probable that the sources are separate formations, as there are distinct differences in the number and quality of the accompanying minerals, and the diamonds themselves differ in shape and character. The grupiaras of the Pardo district are similar to those of the Diamantina district of Minas Geraes, and they each contain quartz, yellow and red fragments of monazite crystals, white and brown zircon, cyanite, staurolite, almandine, titanite, magnetite, and pyrite, but corundum, which is found in no other Brazilian diamond field, occurs with the diamonds in the Pardo district. On the other hand, the Pardo fields are said to contain no anatase, tourmaline, hydro-phosphate or itacolumite. The diamonds also, unlike those of other fields, are octahedral, whereas the usual form of Brazil stones is cubic. In the Paraguassu district, the crystals are irregular and distorted; in Minas Geraes they are regular and cubic ; in the Pardo fields, regular and octahedral. The diamonds of the Paraguassu, where carbons are found with them, though more brilliant, are not as clear as those of the Cannavieiras or Pardo region, where carbons do not occur. There are other differences. Bagagem yields the largest and best crystals. The crystals of the Bahia fields run smaller than those of Minas Geraes and carry more color. It is a peculiar fact that many of the colored Brazilian crystals cut white, even of those which in the natural state appear to be of sufficiently deep color to class as fancies. Some of the crystals have cavities which look like pumice stone. Surface impressions of other minerals in the natural facets are of frequent occurrence, many of them resembling the form of quartz crystals. Stones that will cut to fancy diamonds like those of Borneo and the Dutoitspan mine of the Kimberley group, are rare.

Diamonds of large size are seldom found in Brazil. Few have been found worthy of mention when compared with the numerous large crystals of Africa. The largest on record was found in Minas Geraes and weighed 254 1/2 carats or about one-twelfth of the weight of the Cullinan and a little over a quarter of the size of the Excelsior. Since, one of 138 carats was found on the Rio Abaéte; one of 1203/8 at Bagagem and one of 107 carats at Tabacos on the Rio das Velhas. Most of the crystals run from 1/4 to 1/2 carat. Though published reports from the Brazilian fields have always been untrustworthy, owing to the prevalence of smuggling, they give some indication of general conditions. Ac-cording to the declarations made, only 80 stones of one oitava (17 1/2 carats) and over, were found in the fifty years prior to 1830. In the best years of Diamantina, two or three stones only of 16 to 20 carats each were declared annually out of ten thousand.

The Pardo fields are said to be very unhealthy, but in the mountains of the Paraguassu and Minas Geraes districts, a foreigner, if careful, may escape the diseases of the lower lands. J. C. Branner claims that the catingacovered highlands of Bahia, though hot, are as healthful as any in the world. The richest fields of Bahia were on the east side of Serra do Sincorâ where the Paraguassu and Andarahy cut through the mountains. Late reports indicate that there are rich deposits yet farther back in the mountains.

The general character of the Brazilian diamond fields indicate a wide upheaval of the basic granite rock leaving a very rough and broken surface full of huge gullies and fissures. In these fissures, and in basins or depressions in the granite, are deposits of disintegrated material forming sandstones and conglomerates of varying hardness, in which the diamonds occur. These deposits have in a large measure been washed from the high places and again deposited in gullies and basins that were the water-levels of the streams ages ago, and parts of these have again been washed down to the banks and beds of the streams which now exist. The diamonds throughout are in an altered material, and the original character of the matrix is not surely known. The indications are that during a period of disruption it was exuded from the interior, since which it has been weathered and washed into a conglomerate of water-worn fragments, and deposited in the process in all the fissures, gullies, depressions and interstices of the surrounding rocks, that lay in the path of the waters to catch it. Of the pink Lavras quartzite beds of the Bahia diamond fields, J. C. Branner says in the Engineering and Mining Journal of May 15, 1909, " Cases of diamonds in place in these quartzites have been reported to the writer, but though he has never personally seen such specimens, the geologic evidence is all in favor of the theory that the diamonds and carbonadoes come directly from the Lavras beds." He gives an analysis of the quartzite by L. R. Lenox as follows: Silica (SiO2) 97.94 per cent. ; Fe203 and Al203 1.98; lime, none ; magnesia, trace; total 99.92.

Mr. Orville A. Derby says of the diamondiferous beds of the Paraguassu district, " These beds, of which the thickness is estimated at more than 500 meters, are profoundly disturbed, being thrown into folds that may be compared to the waves of the sea, and are also cut up by faults with the uplift sides forming enormous steep-faced cliffs." These folds produce a series of outcroppings on the mountain sides and dip now to the east and now to the west. From Santa Isabel to Lencoes, the conglomerate dips to the east, and forms the eastern slope of the range. Over the crest it has a western dip after an interval which exposes a great thickness of the lower sandstone. He says further, " The points of easiest attack thus far worked are insignificant in comparison with the masses of material containing the precious stones still untouched."

All estimates of the quantity of diamonds mined in Brazil and exported are little better than guesses. The government claims ownership of all mines, but is unable to enforce the rights of ownership over the wild and difficult country in which the diamonds occur. It grants concessions, and the district authorities impose and collect taxes where they can, but both are powerless to protect concessioners and licensees against the native garimpeiros, who not only know the country, but the diamondiferous gravels, and are experts at picking the gem out of the material in which it is hidden. With hundreds of square miles of broken country covered with dense forest and jungle in which to roam; their only implements a wooden bowl in which to wash the cascalho and a little wooden bottle to hold the diamonds ; undiscoverable hiding places on every hand, these men can work any part of a concessioner's territory but the one spot in which he has his men working, without fear of detection. There are no means of ascertaining the quantity of diamonds obtained in this way. The only real statistics are the declarations made for exportation and as the government imposes an export duty, it is well known that a part only of the diamonds exported are declared. From records made by a mine owner in Diamantina in 1906 it appears that the output of that district by lawful miners at that time was about 5,000 carats per month. These were reported as worth $40 per carat, but it is very doubtful if they realized nearly so much. Rough to command that price must be very good and though many of the diamonds of Minas Geraes are fine, the larger part are small or of poor quality, so that the average value could not exceed that of mines like the Wesselton and Jagersfontein of Africa, for instance. In that year the value of diamonds and carbons together, exported from Brazil, according to government statistics, was $310,000. In 1905 it was only $150,000. In 1890, before the African Syndicate had forced up the price of diamonds, the Minas Geraes output was said to be about 1,000 carats only.

The production of the mines of Salobro, Cannavieiras district, for the ten years ending 1890 was estimated at 193,644 grams. Although this region is not hilly, it is difficult to work, as it is covered with a dense forest growth, and the diamondiferous deposit lies usually about two feet under the surface. The conglomerate which carries the diamonds outcrops in the beds of the Salobro river and its tributaries, and some think that the whole region, back to the Pardo and Jequetinhonha rivers, has an understratum of the diamondiferous deposit. Several French and English companies have worked these Salobro mines for years at a profit.

Authorities conflict regarding the output of the Brazilian mines in the early years after their discovery. Up to 1740 estimates of the yearly production vary from 20,000 to 144,000 carats. From 1740 to 1772 the official reports gave an average production of about 52,000 carats per annum.

Then the government began to work the mines, much after the saine methods pursued by the lessees, but guarding the diamondiferous districts with soldiers, to prevent ingress or egress of any not employed or properly accredited, and to arrest smugglers. The inhabitants even could not cross the line without a written permit, and everybody on leaving the diamond district was searched. If a smuggler was caught, his property was confiscated and he was sentenced to imprisonment, the soldier being rewarded. Notwithstanding the utmost watchfulness, smuggling was practiced on a large scale, probably with some connivance on the part of officials, and the contraband stones were usually above the average in size and quality. The cost of operation to the government was excessively high. For several years four to five thousand negroes were employed, but the number dwindled by 1808 to about one thousand. From 1772 to 1818, while the mines were under government administration, they are said to have yielded 1,298,037 carats, the best year being 1784, with an output of 56,-145 carats, and the poorest 1818, with a production of 9,396 carats only. In round figures, the production, without guessing as to the amount taken by smugglers, has been estimated from the discovery to 1818, as follows : from the beginning to 1740, 240,000 carats. From 1740 to 1772, 1,700,000 carats, and from 1772 to 1818, 1,300,000. In all up to 1818, 3,240,000. Some authorities place the quantity produced through legitimate channels up to 1822 at a little under three million carats. The production, however, between 1818 and 1822 was small, having fallen to about 12,000 carats annually.

There appears to be little definite knowledge of the output from 1818 to 1850, but writers generally agree in putting the entire product of the Brazilian mines up to 1850 at a little over 10,000,000 carats, of which some-thing over 5,800,000 is credited to the Minas Geraes district, nearly 1,200,000 carats to Matto Grosso, and over 1,200,000 to Bahia.

The discovery of very rich deposits in the Serra do Sincorá, Bahia, in 1844, drew thousands to these fields and the neighborhood of the rivers Paraguassu and Andarahy, where they cut through the mountains, was worked so diligently that for some time the daily out-put averaged between fourteen and fifteen hundred carats. As the exposed gravels were exhausted and it be-came more difficult to reach the diamondiferous material, the number of workers dwindled, and with them the production. The Bahia fields were constantly extended, however, so that by 1858 the production of Bahia was 54,000 carats as against 36,000 carats for Minas Geraes.

In 1850 and 1851 the Bahia yield was said to be about 300,000 carats per annum, but from that time, the average yearly production fell about half, though it recovered somewhat in the early sixties. From 1850 to the discovery of diamonds in Africa, the Brazil output amounted in round figures probably to 3,000,000 carats. After that it became an unimportant factor in the diamond market, though impetus has been given to the industry of late years by the high prices which the London Syndicate established for diamond rough, and the demand for carbon, which is found in connection with the diamonds suitable for cutting, in Bahia only. From 1870 to the present it is doubtful if the entire Brazilian diamond and carbon output much exceeded a yearly aver-age of i 00,000 carats.

The impetus given to the industry by the general prosperity of the opening decade of the twentieth century is indicated by the Consular reports, which give the production of the State of Bahia as 154,307 carats in 1906; 189,949 carats in 1907 and 298,046 in 1908. It is estimated that the entire output of the Bahia fields to the end of 1908 amounts to 12,351,576 carats.

When the market was first flooded with African diamonds, the Brazilian output dwindled rapidly. Not only could the African mines fully supply the world's rapidly increasing demand, but the Syndicate in London controlled the channels of trade. The unhampered sale of African rough in the beginning, rendered the Brazilian industry, if conducted on a large scale, unprofitable, and it is possible that one reason for the caution of the Syndicate in making their first advances in price, was to avoid encouraging a resumption of mining in Brazil. Not until late in the nineties, when the price of rough had been doubled, was there a revival of interest in the Brazilian fields. Since then, the good price obtainable for diamond rough and carbon has given a stimulus to the industry, and considerable outside capital has been enlisted in developing new fields or working over the old ones, though some of the new companies formed for that purpose, in the United States especially, have not as yet got much beyond enlisting the capital. Withal, the output 0f the Diamantina region is given in consular reports as averaging about 5,000 carats per month only during 1906.



Home | More Articles | Email: info@oldandsold.com