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and perpendicular rocks which the natives call buffas, covers in many places the clay slate, especially on the side of the Villa de Xeres, where a mountain rises in the midst of these porphyritic formations, in the form of a bell, the basaltic cone of the Campana de Xeres. Among the secondary rocks of Zacatecas we observe, near the amalgamation works of la Sauceda, compact limestone, in which Mr. Sonneschmidt also discovered Lydian stone, an old freestone (urfelsconglomerat) containing fragments of granite*, and a clayey and felspar agglomeration which is easily confounded with the grauwakke of the German mineralogists. The presence of the Lydian stone, with limestone, might tempt~us to believe that this last rock belongs to transition limestone (ubergangs kalkstein) which appears at the surface in the Cerro de la Tinaja, eight leagues to the north of Zacatecas; but I must observe here, that on the coast of South America, near the Morro of New Barcelona, I found kiesel slate forming subordinate beds in a limestone which was undoubtedly secondary.
The savage aspect of the metalliferous mountains of Zacatecas, are a singular contrast to the great wealth of the veins which they con
* In the Ravin leading from Zacatecas to the content of Guadalupe. -.
tain. This wealth is displayed, and the fact is very remarkable, not in the ravins, and where the veins run along the gentle slope of the mountains, but most frequently on the most elevated summits, on points where the surface appears to have been tumultuously torn, in the antient revolutions of the globe. The mines of Zacatecas produce yearly at an average, from 2500 to 3000 bars of silver, at 134 marcs each*.
The mass of the veins of this districtt con ■ tains a great variety of metals, viz: quartz, splintery hornstone, calcareous spar, a little of the sulfate of baryte and brown spar; prismatic black silver called in the country azul acerado; sulfuretted silver, (azul plomilloso) mixed with native silver; fuligenous silver (the silberschrvartze of the Germans, polvorilla of the Mexicans); pearl grey, blue, violet, and leek green muriated silver, (plata parda azul y verde) at very inconsiderable depths, a little red silver (petlangue or rosicler); and native gold, parti- * From 219,866 to 263,839 lib. Troy. Trans.
f Sonneschmidt, p. 185. The minerals called by the inhabitants of Zacatecas copalillo, metal cenizo, and metal azul de pldta, appear to this mineralogist mixtures of galena, sulfuretted silver, and native silver. I have thought proper to insert these synonimes of the Mexican minerals, because their knowledge is very important to the mineralogies! traveller. See Garces, Nueva Theoria del beneficio de hs metaks, p, 87,124, and 138.
cularly to the south west of the town of Zacatecas; argentiferous sulfuretted lead (soroche phmosa rehiciente y tescatete); carbonated lead; black, brown, and yellow sulfuretted zinc, (estoraque and ojo de vivora); pyrite of copper and iron (bronze nochistle, or dorado, and bronze chino); magnetieal oxydulated iron; blue and green carbonated copper, and sulfuretted antimony. The most abundant metals of the celebrated vein called the veta qrande, are prismatic black silver (sprodglaserz), sulfuretted ro vitreous silver, mixed with native silver and silberschwarze.
The lntendancy of Zacatecas contains the mines of Fresnillo, and those of Sombrerete. The former are very feebly wrought, and are situated in an insulated group of mountains, which rise above the plains of the central table land. These plains are covered witJi porphyritic formations; but the metalliferous group itself is composed of grauwakke. According to the observation of M. Sonneschmidt, the rock is traversed there by an innumerable quantity of veins, rich in grey and green muriated silver. The mines of Sombrerete have become celebrated, from the immense riches of the vein of the veta negra, which in the space of a few months left to the family of Fagoaga, (Marques del Apartado) a net profit of more than 20 millions of livres tournois*. The most part of these veins are found in a compact limestone, which contains like that of the Sauceda kiesel slate, and lydian stone. The dull red silver particularly abounds in this district of mines; and it has been seen to form the whole mass of the veins which have more than a metre in extent f (puissance). Near Sombrerete the mountains of secondary calcareous formation, rise much above the porphyritic mountains. The Cerro de Papanton appears to be more than 3400 metres J, above the level of the sea.
The mineral depository of Catorce, holds at present the second or third rank among the mines of New Spain, classing them according to the quantity of silver which they produce. It was only discovered in the year 1778. This discovery, and that of the veins of Gualgayoc, in Peru, vulgarly called the veins of Chota, are the most interesting in the history of the mines of Spanish America, for the last two centuries. The small town of Catorce, the true name of which is la Purissima Conception de Alamos de Catorce; is situated on the calcareous table land, which declines towards the nuevo reyno de Leon, and towards the
* £ 833,400 Sterling. Trans. f More than 3 feet 3 inches. Trans. % 11,184 feet. Trans. VOL. III. P
province of New Santander. From the bosom of these mountains * of secondary compact limestone, masses of basalt, and porous amygdaloid rise up as in the Vicentin, which resemble volcanic productions, and which contain olivine, zeolite, and obsidian. A gTeat number of veins of small extent, and very variable in their breadth and direction, traverse the limestone, which itself covers a transition clay state; and the latter perhaps is superimposed to the syenitic rock of the Buffa del Fraile. The greatest number of these veins are western (spathgdnge); and their inclination is from 25° to 30° towards the north east.f The minerals which form the gangue are generally found in a state of decomposition. They are wrought with the mattock, the pickaxe, and with the bore,' (pointrole.) The consumption of powder is much less than at Guanaxuato, and at Zacatecas. These mines possess also the great advantage of being almost entirely dry, so that they have no need of costly machines to draw off the water.
In 1773, Sebastian Coronado, and Antonio Lianas, two very poor individuals, discovered veins in a situation now called Cerro de Catorce Viejo, on the western slope of the jp»
* Near the mine del Padre Flores, and on the road from San Ramon to Catorce, (Sonneschmidt, p. 279.)
\ Description del Real de Catorce, par Don Jose Manuel Gonzales Cueto, I860 (Manuscript).