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been spread through Europe respecting the contents of the ores of America, I shall proceed to give a more minute description of the districts of mines of Guanaxuato, Tasco, and Pachuca, which I had occasion to visit.

At Guanaxuato, the mine of the Count de la Valenciana produced between the 1st January, 1787, and the 11th June, 1791, the sum of 1,737,052 marcs of silver, which were extracted from 84,368 montones of ores. In the table * containing the general state of the mine, a monton is estimated at 32 quintals, or at 9 o cargas; from whence it follows that the mean riches of the minerals was, twenty years ago, 576 ounces of silver per quintal. Applying the same calculation to the produce of the single year 1791, we shall find 9% ounces per quintal.

* Estado de la mina Valenciana, remitido por mano del Excelleñtiss. Señor virey de Nueva España al Secretario de Estado Don Antonio Valdes. (Manuscript.) I have followed the numbers contained in the table drawn up by Don Joseph Quixano, the administrator of the Valenciana. A nonton (a heap of ores reduced to powder) is reckoned at 35 quintals at Guanaxuato ; at thirty at the Real del Monte, Pachuca, Zultepeque, and Tasco ; at Zacatecas and Sombrerete, at 20 ; at Fresnillo at 18; and at 15 quintals at Bolaños. The carga is generally estimated at Guanaxuato at 14 arrobas ; so that 10 cargas amount there to a monton (Garces, p. 92.) As the wealth of the ore is determined from the contents of the mona ton, the exact knowledge of the measure is of great importance in metallurgical calculations.

At this period, when the mine was in the most flourishing condition, in the total mass of ores there were :

Mar. Ons. Toto of rich ores (polvillos and Xabones,) containing per quintal

22 3 88 of rich ores (apolvillado)

9 3 7800 of rich ores (blanco bueno)

3 1 100g of poor ores (granzas, tierras ordinarias, &c.)

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The quantity of rich ores, was consequently to that of the poor ores, nearly in the proportion of 3 to 14. The ores which only contained 3 ounces per quintal, supplied in 1791 (we are al. ways speaking of the Valenciana mine alone) more than 200,000 marcs of silver, while there was a sufficient quantity of rich ores, (from 3 to 22 marcs per quintal) to yield a produce of more than 400,000 marcs. At present, the mean richness of the whole vein of Guanaxuato may be estimated at 4 ounces of silver per quintal of

The South West part of the vein, which intersects the mine of Rayas, yields, however, minerals, of which the contents generally amount to more than 3 marcs.

In the district of the mines of Pachuca, they divide the produce of the seam of Biscaina into three classes, of which the richness varied

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in 1803, from 4 to 20 marcs per monton of 30 quintals. The minerals of the first class which are the richest, contain from 18 to 20; and those of the second class from seven to ten

The poorest mines which form the third class are only computed at four marcs of silver per monton. The result is that the good contains from 40 to 57; the middling, from 17 to 27; and the worst about 13'6 ounces of silver per quintal.

In the district of mines of Tasco, the minerals of Tehuilotepec contain in a tarea of four montones or 100 quintals, 25 marcs of silver ; those of Guautla yield 45; their mean wealth is consequently from 2 to 3% ounces of silver per quintal of minerals.

It is not then, as has been too long believed, from the intrinsic richness of the ores, but rather from the great abundance in which they are found in the bowels of the earth, and the facility with which they can be wrought, that the mines of America are to be distinguished from those of Europe *. The three

* The silver ores of Peru do not in general appear to be richer than those of Mexico : The contents are estimated not by the monton, but by the cason (chest) which contains 24 cargas, reckoning each carga at ten arrobas or 2 quintals. At Potosi, the mean richness of the minerals is too ; in the mines of Pasco, lz' ounces per quintal,

districts of mines which we have just alluded to, furnish alone, more than a million of marcs of silver, and from the whole of these data we cannot entertain a doubt that the mean contents of the Mexican ores do not amount, as we have already stated, to more than from three to four ounces of silver, per quintal. Hence these ores, though somewhat richer than those of Freiberg, contain much less silver than the ores of Annaberg, Johann-Georgenstadt, Marienberg, and other districts of the Obergebirge in Saxony. From 1789 to 1799, their have been extracted communibus annis from the mines of the district of Freiberg, 156,752 quintals, which have yielded 48,952 marcs of silver ; so that the mean contents were 2%: ounces per quintal of minerals. But in the mines of the Obergebirge the mean riches have amounted to ten, and at very fortunate periods even to fifteen ounces per quintal.

We have taken a general view of the rocks in which the principal mines of New Spain are found; we have examined on what points, in what latitudes, and at what elevations above the level of the sea, nature has collected the greatest quantity of metallic wealth ; and we have indicated the ores which furnish the immense quantity of silver which annually flows from the one continent to the other. It remains for us to afford some details relative to the most con

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siderable mining operations. We shall confine ourselves to three of these groups of mines which we have already described, to the central group, and those of Tasco and Biscaina. Those who know the state of mining in Europe will be struck with the contrast between the great mines of Mexico, for example those of the Valenciana, Rayas, and Tereros, and the mines which are considered as very rich in Saxony, the Harz, and Hungary. Could the latter be transported to the midst of the great works of Guanaxuato, Catorce, or the Real del Monte, their wealth and the quantity of their produce, would appear as insignificant to the inhabitants of America, as the height of the Pyrenees compared with the Cordilleras.

The Central group of the mines of New Spain, a portion of ground abounding more in silver than any other known on the globe, is situated in the same parallel with Bengal, under a latitude where the equinoctial is confounded with the temperate zone.

This group comprehends the three mining districts of Guanaxuato, Catorce, and Zacatecas, the first of which

possesses an extent of 220, the second of 750, and the third of 730 square leagues, calculating the surfaces from the position of the insulated mines (realitos) at the greatest distance from the chief place of the district. The district of Guanaxuato, the most southern

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