Open main menu

Page:Popular Science Monthly Volume 21.djvu/628

This page has been validated.
612
THE POPULAR SCIENCE MONTHLY.

rounding desert. On the right, toward the east, we may perceive a peak, the summit of which, constantly surrounded with clouds, has never been reached—less on account of its height, which is not much more than six thousand feet, than of the precipices and deep clefts which forbid approaching it. It is the peak of Itaubé. On the left is seen a less elevated mountain, formed of a single block of rounded, rough-grained quartzite, which has been given the name of Pedra Redonda. From around these two peaks rise the principal brooks that, united, form the Jequitinhonha, a stream the sands of which yield diamonds to a considerable distance below Diamantina.

The quartzose rocks predominate everywhere; the schists are seen only at rare intervals, and in their beds. But those rocks, of which quartz in grains forms the principal element, are different from those we have met in the gold-bearing region. They are more granular, only slightly micaceous; they pass into real sandstones; and the beds, generally inclined a few degrees toward the east, are less dislocated, less metamorphic than those of the schists and micaceous quartzites which they cover, and which form an islet on which is situated the city of Diamantina.

To these quartzites and sandstones are added, on the banks of the Jequitinhonha and some of its affluents, conglomerates of rounded pebbles, the horizontal beds of which occur in the same region on the banks of the Paruna, a stream emptying into the Rio das Velhas. The schists and the lower quartzites containing green mica appear around Diamantina, and in patches in the bottom of the ravines through which the Jequitinhonha flows. Quartzites, sandstones superior to the preceding, and conglomerates crowning the whole series, such are the formations, to which heaps and dikes of diorite should be added, which form the soil of this diamond-bearing basin.

The surface, in consequence of the nature of the dominant rock, is covered with a bed of white sand marked by brilliant crystals of quartz derived from the numerous veins of that substance which penetrate all the strata. Of vegetable mold there is not a trace, except in the bottoms of the ravines. In the dry season, a few kylmerias, with knotty trunks and a thick rough bark like that of the cork-oak, humble melastomas with yellow and red petals, and the opuntias, with their straight stems covered with a spiny down, are not sufficient to hide the aridity of the soil. No cultivated fields, but widely scattered houses. Everywhere, however, the ground is dug deeply, and turned over, more by the hand of man than by the action of the elements; but the only product demanded of the earth is the diamond.

The region forms a vast ellipse, the major axis of which, running from north to south, extends about fifty miles from the city of Serro to the little river Caethe Mirim, and the other axis more than twenty-five miles from the Jequitinhonha to a line parallel with the Rio das Velhas. It is, in effect, situated in the valleys of both these rivers,