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the most populous part, the diminution of the produce of smelting is very advantageous to the manufactories which require a great consumption of combustibles. In times of war the want of mercury arrests the progress of amalgamation and compels the miner to endeavour to improve the process of smelting. : M. Velasquez, the director general of the minés, supposed even in 1797, before the discovery of the rich mines of Catorce, where there is nearly no smelting, that of all the minerals of New Spain } were smelted, and the other t amalgamated.
The limits prescribed by us in the execution of this work, do not permit us to enter into any detail of the processes of amalgamation used in Mexico. It may be sufficient to give a general idea of them, to examine the chemical phénomenà which are exhibited in the greatest part of these processes, and to show the difficulties which in the New Continent oppose the introduction of the method invented in Germany in 1786, by Born, Ruprecht, and Gellert. Those who may desire to know thoroughly the practice of American amalgamation, will find the most satisfactory information in a work which M. Sonneschmidt proposes to publish. This worthy mineralogist resided in New Spain for the space of twelve years; he had oecasion to submit a great number of minerals to amalgamation; and he had it in his power
to discover by his own experience, the advantages and disadvantages of the different methods which have been followed since the sixteenth century in the mines of America.
The antients knew the property which mercury possessed of combining with gold; and they made use of amalgamation in gilding copper, and collecting the gold contained in their worn out dresses, by reducing them to ashes in clay vessels *. It appears even certain that, before the discovery of America, the German miners used mercury not only in washing auriferous earths, but also in extracting the gold disseminated in veins t, both in its native - state, and mixed with pyrites of iron, and with
the ore of grey copper. But the amalgamation of silver minerals, and the ingenious process now used in the New World, to which we owe the greater part of the valuable metals existing in Europe, or which have flowed from
* Plin. XXXIII, 6. Vetruv. VII. 8. Beckmann's Gesch. der Erfindungen, B. I. p. 44 ; B. III. p. 307 ; B.IV.
† For example, at Goldcronach, in the Fichtelgebirge, where they still shew the situation of the old amalgamation mills (quickmühlen) for the braying of the auriferous minerals. Valuable documents, have been found in the archives of Plassenbourg, which I had occasion to study during a long residence in the mountains of Steeben, and Wunsiedel, that prove the antiquity of the amalgamation works at Goldcronach.
Europe to Asia, goes no farther back than the year 1557. It was invented in Mexico by a miner of Pachuca of the name of Bartholome de Medina. From the documents preserved in the archives of the despacho general de Indias, and from the researches of Don Juan Diaz de la Calle*, there cannot remain a doubt as to the true author of the invention, which has sometimes been attributedt to the canon Henrique Garces, who in 1566, began to work the mercury mines of Huancavelica, and sometimes to Fernandez de Velasco, who in 1571 introduced the Mexican amalgamation into Peru. It is not so certain however, that Medina, who was born in Europe, had not already made experiments in amalgamation before coming to Pachuca. Berrio de Montalvo, an alcalde de corte at Mexico I, and author of a Memoir on the metallurgical treatment of silver minerals, affirms, “ that Medina had heard in Spain that silver might be extracted by means of mercury and common salt ;" but this assertion is sup
* Memorial dirigido al Señor Don Felipe IV. (Madrid 1646) p. 49. Garces, del beneficio de los metales, p. 76–82.
+ Solorzano, Politica de las Indias, lib. vi. c. vi. n. 17. Garcilasso, P. I. p. 225. Acosta, lib. iv. c. ii. Lampadius Handbuch der Hüttenkunde, B. i. p. 401.
Informe al Excellentiss Señor Conde de Salvatierra, virey de Mexico, sobre el beneficio descubierto' por el Capitan Pedro Mendoza Melendez y Pedro Gurciu de Tapia (Mexica 1643) p. 19.
ported by no convincing proof. Cold amalgamation was found so profitable in Mexico, that in 1562, five years after the first discovery of the process of Medina, there were already 35 works at Zacatecas* in which minerals were treated with mercury, notwithstanding Zacatecas is three times further from Pachuca, than the old mines of Tasco, Zultepeque, and Tlapujahua.
The Mexican miners do not appear to follow any very fixed principle, in the selection of the minerals submitted to smelting or amalgamation; for we see them smelt in one district of mines, the same mineral substances which in another they believe can only be managed with mercury. The minerals which contain muriate of silver, for example, are sometimes smelted with carbonate of soda (tequesquite), and sometimes destined to the processes of hot and cold amalgamation; and it is frequently only the abundance of mercury, and the facility in procuring it, which determine the miner in the choice of his method. In general they find it necessary to smelt the very rich meagre minerals, those which contain from ten to twelve marcs of silver per quintal, argentiferous sulfuretted lead, and the mixed minerals of blende and vitreous copper. On the other hand, they
* Descripcion de la ciudad de Zacatecas, por el Conde de Santiago de la Laguna, p. 42.
find it profitable to amalgamate the pacos or colorados*, destitute of metallick lustre; vitreous red black and horned native silver ; fahlore rich in silver; and all the meagre ores which are disseminated in very small parcels in the gangue..
The minerals destined for amalgamation must be triturated, or reduced to a very fine powder, to present the greatest possible contact to the mercury. This trituration under the arastras or mills, of which we have already spoken, is of all the metallurgical operations that which is executed in the greatest perfection, in the most part of the Mexican works. In no part of Europe have I ever seen mineral flour or schlich so fine, and of so equal à grain, as in the great haciendas de plata of Guanaxuato, belonging to Count de la Valenciana, Colonel Rul, and Count Perez Galvez. When the minerals are very pyritous, they are burnt (quema) in the open air in heaps, on beds of wood, as at Sombrerete, or in schlich in reverberating furnaces (comalillos). The latter I found at : Tehuilotepec: they are 12 metres* in length,
* Alvaro Alonzo Barba, el arte de béneficiar metales, 1639, Lib. ii. c. iv. Felipe de la Torre Barrio y Lima, minero de San Jnan de Lucanas, tratado de azogueria (Lima 1738). Juan de Ordoñez, Cartilla sobre el beneficio de azogue (Mexico 1758). Francisco Xavier de Soria, Ensayo de metalurgia (Mexico 1784).
+ 38 feet. Trans.