ARGENTIFEROUS GALENA.—CERUSITE. 37 
greatest interest, especially in connexion with the analyses of the ore, I quote the observations 
upon the locality given in the Report: 
“ The want of means to open these mines, and the ignorance of mining characteristic of the 
New Mexican,have altogether prevented any development of their richness; and it has only been 
within the last eighteen months that anything like a serious commencement has been made. 
Mr. Stevenson has opened a mine about fifteen miles from the river, at Dona Ana, and, notwith¬ 
standing the impossibility of getting an experienced miner, and the crude and imperfect man¬ 
ner of smelting he has been compelled to adopt, the results have been exceedingly profitable. 
The ore is powdered between two stones, and the smelting is done without one convenience 
common to the States. The refuse, probably, contains as much silver as the original ore; and, 
notwithstanding this, from a mule-load of three hundred pounds of the ore, he gets $18 of 
silver.” 1 
These descriptions will apply to a silver mine rather than to one of lead. The specimens 
brought in are of lead, and contain but a small portion of silver. It is, however, possible that 
there is a large quantity of loose friable ore in connexion with the more compact masses, such 
as Captain Pope obtained, and which is much more rich in silver. Silver is a common associ¬ 
ate of lead ores, especially of galena, with which it is so combined that it is generally separated 
by smelting and cupellation. The following is the description of the specimens : 
No. 78. Galena, from Organ mountains ?—The specimen is a very fine mass of galena, (a 
sulphuret of lead,) and it contains a small nodule of iron pyrites, and some fragments of car¬ 
bonate of lead. Galena, when pure, consists of— 
Sulphur. 13.4 
Lead. 86.6 
100.0 
It crystallizes in cubes and in modifications of the monometric system, the cleavage of which 
is very distinct in the specimens. This ore of lead generally contains a small quantity of silver, 
and the specimen is labelled “ argentiferous.” The specimen was examined by cupellation to 
determine the quantity of silver. An average of three trials yielded 0.165 per cent., or 48 troy 
ounces to the ton. It yielded 85.62 per cent, of lead. 2 
No. 79. Cerusite, (specimen marked IC Plornb argentifere,”) from the same locality as No. 73.— 
This is a mass of compact carbonate of lead, containing some small cavities in which the crys¬ 
talline planes of the mineral can be seen. The amount of lead was determined as sulphate, 
giving 72.48 per cent, of the metal. An examination was made for silver, but not a trace could 
be found. 
Carbonate of lead is known in mineralogy under the name of cerusite , and, when pure, has 
the following composition : 
Carb onic acid.. 16.5 
Oxide of lead... 83.5 
100.0 
This mass is remarkably large, and shows that very considerable deposits of ore exist at the 
locality from which it was taken. The mineral has resulted from the decomposition of the 
vein, which probably consists of the sulphuret. It is a very valuable ore of lead, and is very easily 
1 Report of Captain Pope, p. 31. 
2 The examination of these specimens for silver was made for me by Doctor J. D. Easter, of Baltimore. 
