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are most frequent in the province of Oaxaca,. either in gneiss or micaceous slate (glimmer; schiqfer). This. last rock is particularly richin. gold, in the celebrated, mines of Rio San, Antonio. These veins, of which the gtangue. is milk quartz, are more than half a. metre in

thickness ", but their richness is very unequal.

They are frequently strangled, and the extrac

tion of gold in the mines of Oaxaca, is in general by no means considerable. The same

metal is to be found either pure or mixed with. silver ore, in the greatest number of veinsfl which have been wrought in Mexico; and.- there is scarcely a single silver mine which

does not also contain gold. Native gold is frequently. found crystallized. in octahedrons,. or as lamina, or in a. reticulated form,. in the. silver ores of the mines of Villalpando. and> Rayas near Guanaxuato, in those of Som--_ brero (intendancy of Valladolid), Guarisameyi to thewest of Durango, and Mezquital in their province of Guadalaxara. The gold of. Mez-quital is looked upon as the purest, that isto say, as being least alloyed with silver, iron,

and copper. _The principal vein in the mine’ of Santa Cruz, at Villalpando, which I visited: in themonth of September 1808, is traversed

by a greatnumber of small rotten. veins, (hilosl

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gillaceous 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 them-
selves in large vessels, to prevent any of the
auriferou-s clay from being carried ofi' bythem
on their bodies. The silver ore of Villalpando ge-
nerally contains‘ only two ounces of gold per load,

-(carga of 12 arrobas); but -it frequently contains

even eight -or ten ounces per load, or 1,3, ounces
per quintal. - It may be of use to mention here
that at the H arz, 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, 1' . ‘

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,15o _ POLITICAL Essay on THE [noox Ill,

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 Taddé. 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 180 to 1.50 francs. I shall
examine in another place the quantity of platina,

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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 popu-
lar 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 fizklerz
(grey-copper) of Guadalcanal in Spain. g

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 ana-
logy to those of Saxony, the Harz, and Hun-
gary. 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 govern-
ment 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 platinais found in Chopo, (Choco P) at Barbados, (Barhacoas ?) and at Carthagena a sea port, a hundred and thirty leagues distant from the gold lavaderos of Taddo. 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-,1, grains ; and-its specific weight, is according to M. Tralles, 18,947. (Karsten, Min. Tabellen, 1808, p. 96.)

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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 df 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, Beitriige zur chemischen Kenntniss der Mineral Kiirper, b. iv. § 4».

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