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del desposorio) of exceeding richness. The argillaceous loam, with which these small veins are filled, contains so great a quantity of gold disseminated in impalpable particles, that the miners are compelled, when they leave the mine nearly in a state of nakedness, to bathe themselves in large vessels, to prevent any of the auriferous clay from being carried off by them on their bodies. The silver ore of Villalpando generally contains only two ounces of gold per load, (carga of 12 arrobas); but it frequently contains even eight or ten ounces per load, or 1', ounces per quintal. It may be of use to mention here that at the Harz, the pyrites of the Rammelsberg, contains only a 29 millionth part of gold, which is however extracted with profit. *

The District of the mines of Guanaxuato, has furnished according to the registers of the Provincial Treasury, +

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* Brangniart, Minéralogie, t. ii. p. 345.

Estado de la Tresoreria pincipal de Real Hacienda de Guanatuato, del 21 de Novembre de 1799, (M.S.)

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The result of this table is that the silver extracted from the vein of Guanaxuato, contains from one to three thousand parts of its weight · in gold.

Platina is erroneously stated to be found in the auriferous sands of Sonora. This metal has never yet been discovered to the north of the Isthmus of Panama, on the Continent of North America. Platina in grains is only found in two places of the known world ; in Choco one of the provinces of the kingdom of New Granada, and near the shores of the South Sea, in the province of Barbacoas, between the 2° and 6° of north latitude. It is peculiar to the alluvial soil of a surface of 600 square leagues, the extent of which is scarcely equal to two of the departments of France. The stream-works (lavaderos), which at present yield the greatest quantity of platina, are those of Condoto, Santa Rita, or Viroviro, and Santa Lucia, and the Ravin (quebrada) of Iro, between the villages of Novita and Taddo. There are several gold stream-works in Choco, (for instance, those of the districts of San Augustin and Guaicama,) where no trace of platina is to be found. The price of this metal in grain on the spot is eight piastres, or 40 francs the pound, while at Paris it is generally from 130 to 150 francs. I shall examine in another place the quantity of platina,

which in the present state of the mines of Choco, America can furnish to Europe. It is also an absolutely false assertion, that platina has ever been found near Carthagena or Santa Fe, at the Islands of Porto Rico and Barbadoes, and in Peru*, although these different localities are pointed out in the most esteemed and popular works. Perhaps it will one day be proved by chemical analysis, that platina exists in several silver ores of Mexico, as it exists in the fahler% (grey-copper) of Guadalcanal in Spain.

The silver supplied by the veins of Mexico, is extracted from a great variety of ores, which from the nature of their mixture, bear an analogy to those of Saxony, the Harz, and Hungary. The traveller must not expect to find a complete collection of these ores in the school of mines of Mexico. The mines being all in the hands of individuals, and the Mexican government possessing but a very feeble influence on

* Hauy Mineralogie, t. iii. p. 370. In a memoir inserted in the Anales de Ciencias Naturales, published by the Abbé Cavannilles, we read that platina is found in Chopo, (Choco ?) at Barbados, (Barbacoas ?) and at Carthagena a sea port, a hundred and thirty leagues distant from the gold lavaderos of Taddò. Yet more than 18 years ago, M. Berthollet communicated a very accurate account of the places where platina is procured (Annales de Chimie, Juillet 1792) I brought to Europe a pepita of platina of an extraordinary size. It weighs 1088% grains ; and its specific weight, is according to M. Tralles, 18,947. (Karsten, Min. Tabellen, 1808, p. 96.)

the administration of the mines, it was not in the power of the professors to collect whatever had any

relation to the structure of veins, beds, and masses of ores. At Mexico as well as Madrid, the public collections contain the rarest minerals of Siberia and Scotland, while we vainly seek what might throw light on the mineralogical geography of the country. We must hope that the cabinet of the school of mines will become gradually richer, when the pupils of this fine establishment shall be sent into the most distant provinces from the capital, and have proved to the proprietors of mines how much it is for their interest, that the means of instruction should be facilitated. Without a knowledge of the localities in detail, and without a deep study of the minerals of which the mass of the veins, or the contents of the lodes and beds are composed, all the changes which may be proposed for the improvement of the process of amalgamation, will turn out mere chimerical projects.

In Peru, the greatest part of the silver extracted from the bowels of the earth, is furnished by the pacos, an ore of an earthy appearance, which M. Klaproth was so good as to analyse at my request *, and which consist of

Klaproth, Beiträge zur chemischen Kenntniss der Mineral Körper, b. iv. $ 4.

a mixture of almost imperceptible particles of native silver, with brown oxyde of iron. In Mexico, on the other hand, the greatest quantity of silver annually brought into circulation, is derived from those ores which the Saxon miner calls by the name of dirre erze * especially from sulphuret of silver, (or vitreous silver) from arsenical (fahlerz), and antimonial grey copper, (grau or schwarzgiltigerz) from muriate of silver, (horner%), from prismatic black silver, (sprödglaserz), and from red silver (rothgiltigerz). We do not name native silver among these ores, because it is not found in sufficient abundance to admit of any very considerable part of the total produce of the mines of New Spain being attributed to it.

Sulphuret of silver, and black prismatic silver, are very common in the veins of Guanaxuato and Zacatecas, as well as in the veta Biscaina of Real del Monte. The silver extracted from the ore of Zacatecas, exhibits the remarkable particularity of not containing gold. The richest grey copper, (fahlerz) is that of Sierra de Pinos, and the mines of Ramos. In: the latter, the fahlerz is accompanied with glaserz, with

* See the very instructive work of M. Daubuisson, under the title of Description des Mines de Freiberg. I have followed in the course of this chapter, in whatever relates to the art of mining, and the mode of occurring of minerals, the terminology of M. M. Brochant, Daubuisson, and Brongniart.

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