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I could not see the line of junction of these two limestones, or that of the calcareous formation and the diabasis. The transverse valley which descends from Piedras Negras and the village of San Juan, towards Parapara and the Llanos, is filled with trap-rocks, displaying close affinity with the formation of green slates, which they cover.
In hollowing the new road out of the rock, two large veins of gneiss were discovered in the mica-slate. They are nearly perpendicular, intersecting all the mica-slate strata, and are from six to eight toises thick. These veins contain not fragments, but balls or spheres of granular diabasis,* formed of concentric layers.
I also thought I recognized in these same regions, in the Montana de Avila, and at Cabo Blanco, east of La Guayra, a granular diabasis, mixed with a small quantity of quartz and pyrites, and destitute of garnets, not in veins, but in subordinate strata in the mica-slate. Near Antimano all the orchards were full of peach-trees loaded with blossom.
The strata of the serpentine, where it is stratified with some regularity, run hor. 8, and dip almost perpendicularly. Near the village of San Juan, the granular diabasis appears alone uncovered, and takes a greenish black hue. The feldspar intimately mixed with the mass, may be separated into distinct crystals. The mica is very rare, and there is no quartz.
I remember having seen similar balls filling a vein in transition-slate, near the castle of Schauenstein in the margravate of Bayreuth. The feldspar approximates sometimes to vitreous feldspar when disseminated in very thin laminae in a mass of granular diabasis, decomposed, and emitting a strong argillaceous smell.
This ground is the ancient shore of the great basin of the steppes, and it furnishes an interesting subject of research to the geologist. We there find trap-formations, probably more recent than the veins of diabasis near the town of Caracas, which seem to belong to the rocks of igneous formation.
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