The manner of getting the silver from the ore, or beneficiating it, as it is called in Peru, is this: The ore, after it is dug from the mine and brought to the surface, is broken into pieces about the size of a Madeira nut or English walnut, and sent to the hacienda, in hide-bags, on the backs of llamas or mules. (The hacienda is always situated on the nearest stream to the mine, for the advantages of the water-power in turning the mill.) There it is reduced, by several grindings and siftings, to an impalpable powder. The mill consists of a horizontal water-wheel, carrying a vertical axis, which comes up through the floor of the mill, the wheel being below. To the top of this axis is bolted a large cross-beam, and to the ends of the beam are slung, by chains, heavy, rough stones, each about a ton weight. These stones, by the turning of the axis, are carried around nearly in contact with a concave bed of smoother and harder rock, built upon the floor of the mill, and through which the axis comes up. The ore is poured by the basket-full upon the bed, and the large hanging rocks grind it to powder, which pours out of holes made in the periphery of the bed. This is shifted through fine wire sieves, and the coarser parts are put in the mill again for re-grinding. The ground ore, or harina, is then mixed with salt (at the rate of fifty pounds of salt to every six hundred pounds of harina) and taken to the ovens (which are of earth) and toasted. I could not learn the quantity of heat necessary to be applied; it is judged of by experiment.
The fuel used in these ovens is the dung of cattle, called taquia; it costs three cents for twenty-five pounds. The ovens here burn one million five hundred thousand pounds yearly. After the harina is toasted, it is carried in hide-bags to the square enclosed in the buildings of the hacienda, and laid in piles of about six hundred pounds each upon the floor. This floor is of flat stones, but should be of flags cemented together; because the stones have often to be taken up to collect the quicksilver, many pounds of which run down between the interstices. Ten of these piles are laid in a row, making a caxon of six thousand two hundred and fifty pounds. The piles are then moistened with water, and quicksilver is sprinkled on them through a woollen cloth. (The quantity of mercury, which depends upon the quantity of silver in the ore, is judged of beforehand by experiments on a small scale.) The mass is well mixed by treading with the feet and working with hoes. A little calcined iron pyrites, called magistral, is also added—about four pounds to the caxon. The pile is often examined to see that the amalgamation is going on well. In some conditions the mass is called hot; in others, cold. The state of heat is cured by adding a little lime and rotten dung; that of cold, by a little magistral or oxide of iron. Practice and experience alone will enable one to judge of these states. It is then left to stand for eight or nine days, (occasionally re-trodden and re-worked,) until the amalgamation is complete, which is also judged of by experiment. It is then carried to an elevated platform of stone, and thrown, in small quantities at a time, into a well sunk in the middle of the platform; a stream of water is turned on, and four or five men trample and wash it with their feet. The amalgam sinks to the bottom, and the mud and water are let off, by an aperture in the lower part of the well, into a smaller well below, lined with a raw-hide, where one man carries on the washing with his feet. More amalgam sinks to the bottom of this well, and the mud and water again flow off through a long wooden trough, lined with green baize, into a pit prepared for it, where the water percolates through the soil, leaving the mud to be again re-washed. When the washing is finished for the day, the green baize lining of the trough, with many particles of the amalgam clinging to it, is washed in the larger well. The water, which by this time is clear, is let off, and all the amalgam, called "pella," is collected, put in hide-bags, and weighed. Two caxons are washed in a day. The pella is then put into conical bags of coarse linen, which are hung up, and the weight of the mass presses out a quantity of the quicksilver, which oozes through the interstices of the linen, and is caught in vessels below. The mass, now dry, and somewhat harder than putty, is carried to the ovens, where the remainder of the quicksilver is driven off by heat, and the residue is the plata piña, or pure silver. This is melted, run into bars, stamped according to the ley or quality of the silver, and sent to Lima, either for the mint or for exportation.
In the refining process the fumes of the mercury are condensed, and it is used again. Two pounds, however, are lost to every pound of silver. The proportion of pure silver in the pella seca, or amalgam, after the draining off of the mercury through the bag, is about twenty-two per cent. A careful experiment made by Mr. Galt, a jeweller of this city, on a bit of the pella which I brought home from Cerro Pasco, gave but eighteen and thirty-three per cent. of pure silver.
Salt is worth at this place three reals (37½ cents) the arroba, and mercury costs one dollar the pound in Lima. The superintendent is paid twelve hundred dollars yearly; three mayordomos, thirty dollars each, monthly; the corporals, or heads of the working gangs in the mines, twenty dollars; the miners, sixty-two and a half cents per day, (as much more if they work at night;) and the laborers at the hacienda, fifty cents. This, however, is nominal, being more than swallowed up by the supplies. The estimated yearly expenses of these mines are thirty thousand dollars, and the annual yield, seventy thousand dollars. A caxon, of six thousand two hundred and fifty pounds of the ground ore, yields, by the assay on the small scale, fifty marks, though only twenty-five or thirty are obtained by this process, showing a loss of nearly one-half. The quantity of silver obtained from the relabes, or re-washings, is about twenty per cent. of the whole: that is, if a caxon yield twenty-five marks at the first washing, the re-washing will give five.
An idea may be formed of the value of these mines when I state that at Cerro Pasco, which is seventy-five miles further from Lima, and on the other side of the Cordillera, ore, which yields only six marks to the caxon, will give a profit to the miner, though it is saddled with some duties—such as those for drainage and for public works, from which the ore of Párac is exempt. Malarin, the superintendent, said that the caxon must yield fifteen marks here to pay. But granting this, I do not wonder at his expression, that these mines would in a few years render my countryman, Mr. Prevost, the richest man in the country, ("El hombre mas poderoso, que hay en el Peru,") he owning a third of them.
May 29.—Visited the mines. These are situated down the valley with regard to the hacienda, and are two leagues W. S. W. of it. They are much nearer San Mateo than is the hacienda, but there is no road to them from that village. The road, or rather path, lay along the side of the mountain, and zigzagged up and down to turn precipices, now running near the banks of the little stream, and now many hundreds of feet above it. The ride was bad enough at this time—it must be frightful in the rainy season; though Malarin says he sometimes travels it on horseback. This I am sure I should not do; and when these paths are slippery I would much prefer trusting to my own legs than to those of any other animal. Many persons suffer much in riding amongst these precipices and ravines. Dr. Smith knew a gentleman, who, "familiar with downs and lawns, was affected at the steeps of the Paxaron with a giddiness that for some time after disordered his imagination;" and one of a party of English officers, who crossed the Cordillera at Valparaiso whilst I was there, had to return without crossing, because he could not bear the sight of the sheer descents.
The valley of Párac lies about east and west, and the veins of silver on the sides of the mountains E. N. E. and W. S. W., thus crossing the valley diagonally. There are four mines belonging to the establishment, which employ about sixty workmen, though more could be employed to advantage. These men are directed by a mayordomo and four corporals. They are divided into two gangs for each mine: one party will go on duty at 7 p. m. and work till 5 a. m., when they come out, rest two hours, and go on again till 7 p. m. They are then relieved by the other party. This is very hard work, for the mines are very wet and cold. The getter-out of the ore wields, with one hand, a hammer of thirty pounds, and the carriers of the ore bear a burden of one hundred and fifty pounds from the bottom of the shaft to the surface—a distance in this case of about a quarter of a mile, of a very steep and rough ascent. When I first met one of these men toiling up in the dark, I thought, from the dreadful groans I heard before I saw him, that some one was dying near me; but he does this "a purpose," for when we met he had breath enough to give me a courteous salutation, and beg a paper cigar. Boys commence this work at eight years of age, and spend probably the greater part of their lives in the mine.
The mine called Sta. Rosa, which we visited, has a perpendicular depth of five hundred and twenty feet—that is, the bottom of the shaft, which penetrates the mountain at an angle from the horizon of about 25°, is five hundred and twenty feet below the mouth of it. By the mining laws the shaft (cañon) of the mine must be three feet eight inches high, three feet five inches wide, and arched for security. The superincumbent earth frequently requires to be supported by beams of wood laid against each other in form of Gothic arch. I could not learn how much ore a man could get out in a day, for it is a very uncertain quantity, depending upon the hardness of the rock that encloses the vein. Malarin told us that he had instructed the workmen not to blast whilst we were in the mine, because the dreadful reverberation of sound often had an unhappy effect upon people not accustomed to it, which, as we were men who sometimes dealt in heavy artillery, we did not thank him for.
Returning from the mine we met a drove of llamas on their way from the hacienda. This is quite an imposing sight, especially when the drove is encountered suddenly at a turn of the road. The leader, which is always elected on account of his superior height, has his head decorated with tufts of colored woollen fringe, hung with little bells; and his extreme height, (often six feet,) gallant and graceful carriage, pointed ear, restless eye, and quivering lip, as he faces you for a moment, make him as striking an object as one can well conceive. Upon pressing on him he bounds aside, either up or down the cliff, and is followed by the herd scrambling over places that would be impassable for the mule or the ass.
They travel immense distances, but by short stages—not more than nine or ten miles per day. It is necessary, in long journeys, to have double the number required to carry the cargo, so as to give them relays. The burden of the llama is about one hundred and thirty pounds; he will not carry more, and will be beat to death rather than move when he is overloaded or tired. The males only are worked; the females are kept for the breed. They appear gentle and docile, but when irritated they have a very savage look, and spit at the object of their anger with great venom. The spittle is said to be very acrid, and will raise blisters where it touches the skin. We saw none in the wild state. They are bred on the haciendas in great numbers. We had no opportunity of seeing the guanaco or alpacca, (other varieties of the Peruvian sheep,) though we now and then, in crossing the mountains, caught a glimpse of the wild and shy vicuña. These go in herds of ten or fifteen females, accompanied by one male, who is ever on the alert. On the approach of danger he gives warning by a shrill whistle, and his charge makes off with the speed of the wind. The wool of the vicuña is much finer and more valuable than that of the other species—it is maroon-colored.