Very Large Veins, With An Irregular Direction, Often Assume The Aspect Of Short Layers; And The Balls Of Diorite Heaped Together In Hillocks May, Like Many Cones Of Basalt, Issue From The Crevices.

Mica-slate, chloritic slate and the rocks of slaty amphibole contain magnetic sand in the tropical regions of Venezuela, as in the most northern regions of Europe.

The gannets are there almost equally disseminated in the gneiss (Caracas), the mica-slate (peninsula of Araya), the serpentine (Buenavista), the chloritic slate (Cabo Blanco), and the diorite or greenstone (Antimano). These garnets re-appear in the trachytic porphyries that crown the celebrated metalliferous mountain of Potosi, and in the black and pyroxenic masses of the small volcano of Yana-Urca, at the back of Chimborazo.

Petroleum (and this phenomenon is well worthy of attention) issues from a soil of mica-slate in the gulf of Cariaco. Further east, on the banks of the Arco, and near Cariaco, it seems to gush from secondary limestone formations, but probably that happens only because those formations repose on mica-slate. The hot springs of Venezuela have also their origin in, or rather below, the primitive rocks. They issue from granite (Las Trincheras), gneiss (Mariara and Onoto) and the calcareous and arenaceous rocks that cover the primitive rocks (Morros de San Juan, Bergantin, Cariaco). The earthquakes and subterraneous detonations of which the seat has been erroneously sought in the calcareous mountains of Cumana have been felt with most violence in the granitic soils of Caracas and the Orinoco.

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