A Few Strata Of Gneiss Abound In Silvery Mica, And Contain, Instead Of Garnets, An Immense Quantity Of Small Octohedrons Of Pyrites.

This silvery gneiss resembles that of the famous mine of Himmelsfurst, in Saxony.) It appears that the gneiss of the Cerro de Chacao also furnishes another metallic deposit, a mixture of copper and silver-ores.

This deposit has been the object of works attempted with great ignorance by some Mexican miners under the superintendance of M. Avalo. The gallery* directed to the north-east, is only twenty-five toises long. (* La Cueva de los Mexicanos.) We there found some fine specimens of blue carbonated copper mingled with sulphate of barytes and quartz; but we could not ourselves judge whether the ore contained any argentiferous fahlerz, and whether it occurred in a stratum, or, as the apothecary who was our guide asserted, in real veins. This much is certain, that the attempt at working the mine cost more than twelve thousand piastres in two years. It would no doubt have been more prudent to have resumed the works on the auriferous stratum of the Real de Santa Barbara.

The zone of gneiss just mentioned is, in the coast-chain from the sea to the Villa de Cura, ten leagues broad. In this great extent of land, gneiss and mica-slate are found exclusively, and they constitute one formation.* (* This formation, which we shall call gneiss-mica-slate, is peculiar to the chain of the coast of Caracas. Five formations must be distinguished, as MM.

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