I had some conversation with the officers respecting the matrix of the diamond, not a vestige of which could I trace. They informed me that they often found diamonds cemented in pudding-stone, accompanied with grains of gold, but that they always broke them out, as they could not enter them in the treasury, or weigh them with matter adhering to them. I obtained a mass of pudding-stone, apparently of very recent formation, cemented by ferruginous matter enveloping grains of gold and diamonds; likewise a few pounds of the _cascalho_ in its unwashed state.
This river, and other streams in its vicinity, have been in washing many years, and have produced great quantities of diamonds, which have ever been reputed of the finest quality. They vary in size; some are so small that four or five are required to weigh one grain, consequently sixteen or twenty to the carat: there are seldom found more than two or three stones of from seventeen to twenty carats in the course of a year, and not once in two years is there found throughout the whole washings a stone of thirty carats. During the few days I was here they were not very successful; the whole quantity found amounted only to forty, the largest of which was only four carats, and of a light green color.
From the great quantity of _debris_, or worked _cascalho_, in every part near the river, it is reasonable to calculate that the works have been in operation above forty years; of course there must arrive a period at which they will be exhausted, but there are grounds in the neighbourhood, particularly in the Cerro de St. Antonio, and in the country now inhabited by the Indians, which will probably afford these gems in equal abundance.
After residing here five days, we visited a diamond work called Monteiro, about two miles up the river, and went a league further to a gold-work called Carrapato. The _cascalho_ at this work was taken from a part of the river eight feet deep, which formed an eddy under a projecting point; I was shewn a heap of it, that was estimated to be worth £10,000. In removing this heap from its bed, four hundred negroes had been employed three months; and to wash it, would occupy one hundred men for three months more, the expense of both operations amounting to perhaps £1,500. We arrived at this place at eight o’clock in the morning; six negroes were employed four hours in washing two troughs, containing together about a ton of _cascalho_, when, to my great surprise, after the water ran clear, and the large stones were thrown out, the black oxide of iron, of which there was great abundance, was fringed with grains of gold, a novel and very agreeable sight to a stranger. The gold was taken out at three or four different times, and, when the washing was completed, was dried over a fire and weighed: it amounted to nearly twenty ounces Troy. This is esteemed a very rich place, and such circumstances are of rare occurrence. The whole neighbourhood is sterile, presenting the same characteristics as those before described. By proper cultivation the vallies might be rendered very productive; but, as the troops of negroes and their officers are continually changing, no agricultural establishments are formed.
