n . . | | | | |
|Oaxaca . . . . | | | | |
|Puebla . . . . | | | | |
|Queretaro . . . | " | | | |
|San Luis Potosi | | " | | |
|Sinaloa . . . . | " | | | |
|Sonora . . . . | | | | |
|Tabasco . . . . | | | | |
|Tamaulipas . . | | | | |
|Tepic . . . . . | | | | " |
|Vera Cruz . . . | | | | |
|Zacatecas . . . | " | | | |
+----------------+-----------+----------+----------+-------+

The geological formation of the country does not bear special relation
to the deposits of metalliferous minerals, which are distributed in
many parts of the great zone. In general terms it may be said that the
abundance of the ores rather than their richness characterises the
mines of Mexico and is the source of their wealth. Those which have
most steadily produced bullion generally consisted of a main lode
containing enormous quantities of low-grade ore of about 60 ounces per
ton; and typical of these are the mines of Guanajuato, Pachuca,
Queretaro, Zacatecas, and others. The ores, however, are not always
low-grade, for great _bonanzas_ of exceedingly rich ore were
encountered, making rapid fortunes for their discoverers.

_Silver_.--The main lodes in those places enumerated have ranged up to
hundreds of feet in width, and form the most potent silver-ore deposits
upon the globe. Their extensions in length and depth bear out their
importance as metal-producing sources. Thus the Mellado vein, of
Guanajuato, measures, in places, more than 300 feet in width; with
workings ten miles in length, and extending to a present depth of
nearly 2,000 feet. The _Veta Madre_, or "mother lode," ranges from 30
feet to 165 feet in width; whilst others of the famous lodes reach 50
to 100 feet. As to the ore-values, Humboldt, who visited Guanajuato in
the height of its production, at the beginning of the nineteenth
century, assigned as his calculation a value equal to about 80 ounces
of silver per ton _for the whole lode_. For portions of the ore-bodies,
and for many of the great _bonanzas_, much higher values have obtained,
silver up to 7,000 ounces per ton having bee