Leisure hours among the gems

by Augustus C. Hamlin

Some of the diamond mines were of great extent and required many laborers to conduct the operations. That of Mandanga employed twelve hundred slaves in its excavations alone, besides many free persons engaged in other duties. The yield of the Brazilian mines at first was enormous, and one thousand one hundred and forty-six ounces of the precious gem were shipped to Lisbon in one year. The vast quantities of the gem thrown upon the markets brought the price of them down to five dollars per karat.

Consternation speedily spread among the diamond dealers all over the world; and many of them, believing that the gems would soon be as common as transparent quartz, declined to invest largely, even at these low prices. But a panic was checked by the prompt action of the Brazilian Government, in claiming the working of the mines as a royal monopoly, and also regulating the supply. In this condition of affairs the working of the mines and the trade remain at the present day; but the African discoveries and free explorations may change this restriction and monopoly if the Cape fields continue to yield their present supply. According to the estimates of Baron d’Eschwège, the quantity of diamonds obtained from the Brazilian mines under the Government restrictions averaged between 1730 and 1814 thirty-six thousand karats annually, the cost of which amounted to nearly four dollars per karat.

From a variety of causes the supply gradually diminished until about the year 1830, when the diminution was so great, coupled with the increased cost of exploration, that the rough stones cost eight dollars per karat. In 1843 the discovery of the Bahia mines increased greatly the yearly supply, which was then about thirty thousand karats. For two years after the discovery of the Sincora mines the supply amounted to six hundred thousand karats. But the great distance of the mines from the large towns and the coast, the fearful malaria which prevailed in the district, together with the difficulty of obtaining supplies, have prevented the working of the mines to any great extent; and in consequence the supply in 1852 sank to one hundred and thirty thousand karats. In 1732 the price of the rough gem was five dollars per karat, but in three years after it rose to about eight dollars per karat, and remained at that figure as late as 1742.

The Brazilian diamonds are generally very small compared with those yielded by some of the India mines, like that of Gani, which produced a great many gems of ten to forty karats weight. Of the Brazilian yield it was found by Professor Tennant that out of one thousand diamonds, one half weighed less than half a karat; three hundred, less than one karat; eighty, one and a half karats; one hundred and nineteen varied from two to twenty karats, and only one reached twenty-four karats.

Brazil still exports annually diamonds to the value of several millions of dollars, but the exploration has probably been checked by the influx from South Africa and the consequent fall in prices.

Out of the immense number of gems yielded by these mines,—the district of Minas Geraes is said to have produced two tons in weight,—it is strange that more large gems have not been found.

Quite a number of diamonds exceeding fifty karats have been discovered, and several over one hundred karats, the largest being known as the Star of the South, which weighed two hundred and fifty-four karats. This fine gem was found in 1853 in the mines of Begagem by a negress. It was in the form of a dodecahedral crystal. Another fine gem, called the Abaethe, was found in 1797 in the alluvium of the river Abaethe. Three convicts, banished into the interior of the savage country, wandered about from thicket to thicket and mountain to mountain, in hope of discovering some treasure that would restore them again to their friends. After six years of weary wanderings and severe privations they at length stumbled upon a diamond of one hundred and five karats in the bed of the river above named. They ventured to return to the inhabited regions and confided their good fortune to a priest. He took them at once to the Governor of Villa-Rica, who suspended the sentence of the convicts and sent the priest to Rio Janeiro with the gem.

A frigate was despatched with the treasure and the clergyman to Lisbon. The King, delighted with his acquisition, fully pardoned the convicts and advanced the priest to a high rank in his profession.

Many attempts have been made to trace the diamonds of Minas Geraes to primitive and unbroken rocks on the more elevated plateaux or even among the more distant mountains. And sometimes the gems have been found in cascalho at a great elevation, or perhaps in crevices of the sandstones; and hence the idea has arisen that the solid matrix has been found. The cascalho is the true matrix, whether found in the lowlands or on the mountain peaks. The color of this conglomerate is not uniform and varies in many districts. At the rich St. Antonio’s mine it is of a dark gray; at the Veneno it is of a light ochre with lumps cemented with ferruginous oxide; in the Pitanga mine it is of a light gray and almost white, and contains but few diamonds, but of the finest quality. The observer is sometimes led to believe that the abundance of the ferruginous oxide is evidence of the abundance of gems, and this fact is also noticed in the famous mines of Ceylon, where, however, the diamond does not occur.

Concerning the accounts of finding the diamonds in Brazil in their native rock, as described by Claussen and later still by Redington, we are not yet willing to give full credence any more than to the stories of diamonds having been found in the “old rock” in India. We have no doubt of the gem having been found in what appears to be a soft sandstone, but which is in reality a secondary product like the heterogeneous cascalho. And we can conceive this sandstone-like deposit to be formed at the bottom of lagoons under like conditions which gave origin to the conglomerate.