98 GEOLOGICAL REPORT—THIRTY-FIFTH PARALLEL. 
on the southern extension of the Santa Fé and Sandia mountains. Specimens of the ores 
brought in by Captain Pope from his survey along the 32d parallel of latitude are very rich, 
and consist of massive sulphuret of lead, galena, and large masses of carbonateof lead. The 
former contains about forty-eight troy ounces of silver to the ton of ore.! It is probable that 
the mountains around Santa Fé and Albuquerque, and also the Sierra Madre on the west, 
contain many valuable veins of argentiferous lead which have never been discovered. Ca? 
zenus states that several rich silver mines were worked in Spanish times at Avo, at Corrillos, 
and in the Nambe mountains.? Lieut. Abert, when at the village of Manzana, perinde speci- 
mens of silver ores which were taken from mines in the adjoining mountains.? The extensive 
silver mines of Mexico are doubtless in the more highly metamorphosed limestone of the same 
age with that at Santa Fé and along the flanks of the mountains bordering the Rio Grande, 
In passing down the valley of the Hawilhamook, or Bill Williams’ fork, Mr. Marcou observed 
several veins of argentiferous galena, (see notes,) and this led him to believe that silver was 
abundant in those mountains. 
TRON. 
There are several specimens of iron ores in the collection, and it is an interesting fact that 
they are all of the specular or hematite species, although they present very different appear- 
ances. All of the specimens are described in the description of the collection. One is a 
beautifully fibrous variety, and its size indicates that very large masses may be obtained at 
the parent source. Nearly all the specimens appear to have been boulders or loose masses, 
as Mr. Marcou does not give any description of veins or beds. 
Magnetic iron ore occurs in considerable quantity in the pass next west of the Gijón, 
(Williamson's Pass,) where I found large quantities in the bed of a stream coming in from 
the east, mingled with the detritus from the surrounding mountains. 
SALT. 
The inhabitants of the valley of the Rio Grande have long been accustomed to resort to several 
salt lakes, or Salinas, on the east side of the mountains, for their supply of salt. "These lakes 
are about fifty miles east by south from Albuquerque, and one hundred miles south of Santa 
Fé. They are on the high table-lands which extend from the mountains to the Pecos, and 
which are most probably formed by Tertiary strata in that region. The lakes are capable of 
furnishing an almost unlimited quantity of good salt, and the whole adjoiniug country is sup- 
plied from them. I find an interesting account of these lakes given by Gregg. “The largest 
of these Salinas is five or six miles in circumference. The best time to collect the salt is during 
the dry season, when the lakes contain but little water; but even when flooded, salt may be 
scooped up from the bottom, where it is deposited in immense beds, in many places of unknown 
depth, and when dried resembles the common alum-salt. The best, however, which is of superior 
quality, rises as a scum upon the water. A great many years ago, a firm causeway was thrown 
up through the middle of the principal lake, upon which the carretas and mules are driven, and 
loaded with salt still dripping with water. The Salinas are public property, and the people 
resort to them several times a year, in caravans, for protection against the savages of the desert 
in which they are situated. Although this salt costs nothing but the labor of carrying it away, 
the dangers from the Indians, and the privations experienced in an expedition to the Salinas, 
are such, that it is seldom sold in the capital for less than a dollar per bushel. On the same 
great piss, still a hundred miles further south, there is another Salina, of the same character. * 
According to Mr. Marcou, the red marls or clay, near Camp No. 41, are saliferous, and holes 
were found filled with very brackish and magnesian water, which was Diere to the taste. 
Salt was also found in small quantities at several other points. The bed of the dry lake—the 
Soda lake—at the sink of the Mojave, was covered with a saline incrustation, already described. 
! See report on the Geology of the route near the 32d parallel, P. 37, Pacific R. R. Explorations and Surveys, &c. 
? Memoir of a Tour to Northern Mexico, p. 24. * Report of an Examination of New Mexico, p. 487. 
* Commerce of the Prairies, Vol. i, p. 176. 
