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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
gillaceous loam, with which these small veins
-(carga of 12 arrobas); but -it frequently contains
even eight -or ten ounces per load, or 1,3, ounces
The District of the mines of Guanaxuato,
,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
which in the present state of the mines of
The silver supplied by the veins of Mexico,
* 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.)
I52 POLITICAL ESSAY ON THE [noon 1v.
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».