The cinnabar is found in large pockets, or in veins, permeating a kind of trap-rock; and as the miners dig it out, large columns or pillars are left to support the roof, and prevent the chance of its falling in. A small charcoal-fire burned slowly at the base of one of these massive columns, and as its flickering light fell dimly, illuminating with a ruddy glow the bronzed faces and nearly nude figures of the miners, the vermilion hue of the rugged walls and arched roof, sparkling with glittering crystals, forcibly reminded me of a brigand’s cave, such as Salvator Rosa loved to paint.
All the work is done by contract: each gang taking a piece of ground on speculation, is paid according to the amount of ore produced; the ore averaging about thirty-six per cent. for quicksilver, although some pieces that I dug myself produced seventy-five per cent. Many mines in Europe have been profitably worked when the cinnabar has yielded only one per cent.
A shrill whistle rings through the mine; the miners from all directions rush towards the pillars. Thinking, at least, the entire concern was tumbling in, I was about to scamper off, when the guide, seizing my arm, drags me behind a projecting mass of rock, simply saying, ‘A blast!’ For a while there was a deathlike silence—not a sound save the hiss of the fusee, and the heavy breathing of the men; then the cave lighted up with a lurid flash, shedding a blinding glare over every object like tropical lightning. The dark galleries appeared and disappeared in the twinkling of an eye, whilst the report, like countless cannon, was echoed and reechoed through the cavernous chamber. Showers of fragments came rattling down in every direction, hurled up by the force of the powder. On the smoke clearing, the miners set to work to collect the scattered fragments of cinnabar. If a blast has been successful, often many tons of rock are loosened and torn out, to be broken into small pieces and conveyed to the bucket, and hauled by the engine to the surface. The mining operations are continued night and day, seventy-four pounds of candles being consumed every twenty-four hours.
I finish the survey of this singular mine perfectly free from foul air or fire-damp; ascend as I came down; and, by vigorous rubbing with soap-and-water, am slowly restored from bright vermilion to my normal colour.
The ore, on reaching the surface, is conveyed by the tram-cart to the sorting-shed, where it is broken and carefully picked over by skilful hands, great caution being needed in selection, as much valuable ore might be thrown away, or a large quantity of useless rock taken to the smelting-furnaces. The picked ore is placed in large bags made of sheepskin, weighed, and then hauled by the mules to the lower works.
Near the mine is a primitive kind of village, the abode of the miners, sorters, and ore-carriers, who are principally Mexicans; dirty señoras in ragged finery, dirtier children devoid of garments, together with dogs, pigs, poultry, and idle miners playing monte on the doorsteps, contrast sadly with the exquisite little village at the works.
Descending from the mine to the level ground by a short track down the hillside, through scenery indescribably picturesque, I reach the smelting furnaces; these, occupying about four acres of land, are built of brick, admirably neat, and well contrived. As quicksilver is found in several forms—namely, native quicksilver, occurring in small drops, in the pores or on the ledges of other rocks, argental mercury, a native silver amalgam, and sulphide of mercury or cinnabar, different processes are requisite for its reduction. Here it is found solely in form of cinnabar, and to reduce it a kind of reverberatory furnace is used, three feet by five, placed at the end of a series of chambers, each chamber seven feet long, four wide, and five high. About ten of these chambers are arranged in a line, built of brick, plastered inside, and secured by transverse rods of iron, fitted at the ends with screws and nuts, to allow for expansion. The top is of boiler iron, securely luted.
The first chamber is the furnace for fire, the second for ore, separated from the first by a grated partition, allowing the flame to pass through and play over the cinnabar. This ore-chamber, when filled, contains ten thousand pounds of cinnabar. The remaining chambers are for condensing the metal, communicating by square holes at the opposite corners; for instance, the right upper corner and lower left, and vice versâ, so that the vapour has to perform a spiral course in its transit through the condensers. Leaving the chambers, the vapour is conducted through a large wooden cistern, into which a shower of water continually falls, and thence through a long flue and tall chimney carried far away up the hillside.
The mercury is collected, as condensed, in gutters running into a long conduit outside the building, from which it drops into an iron pot sunk in the earth. As the pot fills, the mercury is conveyed to a store-tank that holds twenty tons. So great is its density, that a man sitting on a flat board floats about in the tank on a lake of mercury without its flowing over the edges of his raft. From this tank the metal is ladled out, and poured into iron flasks containing each seventy pounds (these flasks are made in England, and sent to New Almaden): in this state it is shipped for the various markets.
Although every possible care has been taken to prevent the mercurial fumes from injuring the smelters, still a great deal of it is necessarily inhaled, most injurious to health. Clearing out the furnace is the most hurtful process, the men employed working short spells, and resting a day or two between. A furnace charged with ore, I am told, takes about eight days to sublime and cool.