The Silver Mines of Pachuca

THE SILVER MINES OF PACHUCA
By Captain M. Ough Dealy. B.Sc. (Eng.), A.M.I.Mech.E., R.E.M.E.
Extract from R.E.M.E. Journal February 1965

PROLOGUE

Opportunities for members of the British Army to second to the armed forces of other nations are still fairly easy to come by, even in these days of diminishing overseas postings. Although these secondments often mean hard work and little leave, there are other advantages, apart from the additional pay. Until the terms of secondment were reviewed in 1963, it was possible to be granted “end of tour” leave of up to as much as six months, depending on the duration of the secondment contract. This concession was coupled with the choice between a sea passage home or a cash grant, equiv¬alent to the fare, in lieu.

At the end of one such tour of secondment to the Malaysian armed forces, I found I had an entitlement to approximately four months leave and a first class passage from Singapore to the U.K. Extensive enquiries and much cal¬culation showed that it was possible to use the cash grant equivalent of the passage fare in order to return to England, travelling in tourist and economy class, via New Zealand and the Americas.
The problem of accommodation expenses was, fortunately, easily overcome. My father, who is employed in the silver mining industry in Mexico was able to offer accommodation for the duration of our stay there.
Thus it was that in September, 1963, my family and I set sail from Singa¬pore as tourist class passengers for Mexico. The following story is a result of our stay.

INTRODUCTION

The hills are for most of the year a dry nondescript brown, relieved only by the green of the hardy “pirul” tree and the ubiquitous cactus. Outcrops of volcanic rock, with the waste dumps of grey stone and the light brown tailings dams left by the many mining operations, add to the prevailing atmosphere of barrenness. (Fig. 1). The huge pits, cuts and hundreds of tunnel and shaft openings that scar the surface of the land provide further evidence of ex¬tensive mining. But the silence that prevails, and the seeming lack of activity on the surface, give the impression that the miners have stripped the land of its mineral wealth, made what profit they could, and left the hills to the Indians and the ravages of a harsh climate.

A closer look at the area, however, reveals many signs that mining is still active underground. Tucked away, in many of the gulches and “arroyos” (dry river beds) which occur in this rugged land, are mining head frames, and ore bins obviously still very much in use. The silence is still broken by the blast of dynamite, and the noisy movement of trucks and machinery taking ore away for treatment.

A quick examination of the mine workings that exist on the surface will also show that mining in the area has been going on for several centuries. There can still be seen the remains of typically Spanish “haciendas” (com-pounds), much evidence of Cornish mining techniques used in the 1800’s and the more modern head frames and mills of present day practice. It is not diffi¬cult to trace in outline, the history of mining in this district. The many ruins spread over the hills bear mute testimony to the enterprise of the old Spanish
and Cornish miners, whilst the plants and equipment of today are evidence of modem developments.

The extent of the activity on the surface, both past and present, covers a very large area, estimated at roughly 100 sq. Km. The extent of the under¬ground workings, mainly in the form of tunnels, seems even greater to one’s imagination. In their efforts to win the vast fortunes in silver and gold which lay locked in the rock beneath the surface, the miners of the district, using initially crowbars and shovels, and later on dynamite, pneumatic drills and trains, burrowed and cut their way through some 2,000 Km. of workings. The deepest of these extend to about 700 meters below the surface, and one of the most difficult occurred on the edge of a pocket of volcanic activity where the temperature underground produced mine water at almost boiling point.

HISTORY AND DEVELOPMENT

Local legend will have you believe that, shortly after the conquest of Mexico by Cortez in 1521, a band of Spanish explorers had camped one night near the site of what is now the village of Real del Monte some 9 kilometers from the present main centre of mining-Pachuca. They built their campfire near the outcroppings of a vein later known as the “Santa Brigida” vein. The legend goes on to relate that on waking the next morning they saw molten silver run¬ning from the rocks beneath the fire!

Whatever truth there is in this legend, it is certain that Spanish mining activity in this region stems from these very early times. It is also certain that the Indian tribes, particularly the Aztecs, obtained much of their gold and silver from crude workings in this area.

Shortly after the arrival of the Spanish in the area, about the year 1532, a large number of very rich veins were discovered, and over a hundred mines were quickly established. In their quest for wealth, the Spanish employed the most primitive methods by any standards. Safety precautions were unheard of, and power was supplied by animals, or more frequently, by men.

The miners descended into the depths of the mines by means of chicken ladders (made by notching an eight inch tree trunk), along narrow rock trails cut on the edge of an abyss already worked out, down 45 degree inclines and ladders cut in the rock. They broke out the ore by means of a crude crowbar, known as the” barreta” (this was an iron bar with a steel tip requiring frequent sharpening at small underground forges) and see it carried to the surface on the backs of other and possibly less fortunate labourers. The latter were called “tanateros” or burden carriers, and were capable of carrying the most in¬credible loads of ore. In bags made of ox hide or fibre these hardy men (and boys) are known to have carried over 100lbs. of mineralized rock at one go!

Mine ventilation was unknown, lighting was obtained from the feeble flames of tallow candles, and timbering and shoring up of dangerous sections was unheard of. Apart from sandals of rawhide, the miners (mostly Indians) wore little clothing, it being somewhat superfluous in the hot, fetid, underground atmosphere.

The production of the silver and gold from the mineralized rock torn from the ground in this crude fashion, was done in these early days by means of the “patio” process, invented by a Spanish Friar known as Bartolome de Medina. He developed the process in 1557 in the Hacienda “Purisima Grande”, the ruins of which now form part of the Pachuca Tennis Club. This process, although inefficient, was used until early in the present century.

Initially the process involved the crushing of the ore by means of massive wooden stamps shod with heavy iron plates and driven by mules. A finer grind.necessary for a good extraction, was obtained by using “arrastras”¬ clumsy machines which depended upon attrition produced by massive volcanic boulders moved in a circular trough. The stones were attached by chain to a wooden pole, pivoted in the centre of the trough and dragged round by teams of mules which, blindfolded and harnessed to the pole, tramped round pat¬iently in a circle for up to six hours at a time.

The fine dust produced in this primitive manner was then gath¬ered and formed into a “torta”, which can best be described as a large cake of mud, of a diameter of up to 50ft. and a thickness of a few inches. These were laid out in the “patios” (courtyards) and mixed with salt, copper sulphate and mercury, by the trampling of teams of mules. Many of these poor animals were worked until their legs rotted away. However, there is some consolation in knowing that they replaced the barefoot men and boys used initially to per¬form this daily task.

Once amalgamation of the ore in one of these cakes had been achieved, they were cut up into more easily handled sections-referred to in those times as “quesos” or cheeses-stacked on iron shelves and smelted.
In this smelting process large cast iron bells were used to cover the amalgam, whilst heat was applied externally. By using these the mercury was recovered for re-use. Many of them can still be seen flanking the doorways and gates of the various mills and mines of the present day. (Fig. 2).

THE CONDE DE REGLA

It was inevitable, in the circumstances of those days, that a few men would amass tremendous fortunes. One of these, perhaps the most famous, was the Conde de RegIa (Count of RegIa). Of Spanish origin, he arrived in Mexico in the first half of the 18th century, where he initially did well as the head of an uncle’s business, involving mainly the hauling of goods by donkey from Veracruz to various parts of Mexico. His first recorded contact with the mines of Pachuca occurred in 1742, when he assisted in the financing of a low level drainage tunnel in the area.

The tunnel was designed to drain the mines, which by then had been dug so deep as to come up against formidable flooding prob¬lems. At a cost of more than It million pesos (about £1 t million by present day values) and over thirteen years of time the tunnel was eventually com¬pleted. Its success was such, however, that it enabled new veins of very high metal content to be exploited, and its cost was tiny compared with the immense riches that were brought out in the bonanza years which followed. Don Pedro de Terreros-as the Count was known in those days-became almost sole heir to these riches, since his partner in the original enterprise had died before the tunnel was completed. He very quickly became one of the world’s richest men, so rich in fact that it is said that one of his descendants was carried to his christening over a pathway covered in silver ingots from the house to the chap¬el! He was noted for his charity, good works, and as a staunch supporter of the Spanish Crown . . . . so staunch in fact that on a number of occasions he provided funds with which to build galleons and war ships for the Spanish Government. He was created the first Conde de RegIa in 1752, and lived on until 178], by which time he had amassed a fortune of over 15 million pesos, built three haciendas (Fig. 2), a comprehensive mill, and acquired a reputation as the King of Spain’s most loyal and faithful subject.

The death of the Count was followed by relatively lean years in the district. The mines had gone deeper and water had become again a formidable prob¬lem. The political troubles which occurred at the turn of the century, and which incidentally resulted in the War of Independence and finally in freedom from Spanish domination in 1821, brought with them neglect and apathy.

Affairs had reached such a low level in these first years of the 19th century that the mines for a long period were closed.

THE CORNISHMEN MOVE IN

Although the mines had ceased to work, word of their richness had spread to other countries, and aroused considerable interest in England. So much so that it persuaded some English capitalists to enter into negotiations with the third Count de RegIa, to obtain mining rights in the area. A Captain Vetch, of the Royal Engineers, became General Manager of a “Company of Gentle¬men Adventurers” which set out to reopen the mines.

The company set out to equip the mines with the best machinery available at the time. Cornish methods used to recover tin were about the most up to date, and it is not surprising that the company turned to this country for the mach¬inery, skilled miners and techniques it required. Captain Vetch set forth in the company of several hundred Cornish miners and their families, and two ship¬loads of Cornish pump machinery, in the 1820’s for the mines of Pachuca.

It took these intrepid Englishmen a whole year to move their heavy equip¬ment from the then open beaches of Veracruz, through the jungles of the coast, up the steep slopes of the Mexican plateau, to the 10.000£1. elevation of the mines. With remarkable energy and skill they built huge stone buildings to house the cumbersome steam-driven Cornish pumps and hoists, cut a well engi¬neered road (which is still in use) through the barren hills to connect the village of Real del Monte with Pachuca, and after much hard work drained the flooded mines so as to start production again after a lapse of almost a quarter of a century.

The influence and work of these Cornish miners is still very much in evidence today. The gaunt ruins of the typical Cornish pumping houses can still be seen in the hills. (Fig. 3). There are many individuals in the district with blue eyes, fair hair and sturdy build, who cannot speak a word of English, but whose ancestry is as English as that of any Cornishman. One still comes across such Cornish names as Pengelly, Stribley, Penpraze, Trevethon, Rabling, Carne, in this most unlikely part of the world. Even the clock tower in Pachuca reminds one that English influence here was strong-its machinery is English made, and it advertises this fact every quarter of an hour with chimes that are remi¬niscent of those of Big Ben.
Although the Gentlemen Adventurers succeeded in reviving the mines, and obtained large quantities of ore, misfortune seemed to tag their enterprise. So much so, that in 1848, they were forced to sell out to a group of Mexican capitalists at an overall loss of about 10 million pesos. The company sold was by this time known as the “Compana de Real del Monte y Pachuca”, a name which has survived to this day. The change of ownership did not result, however, in the return to England of all the original Cornish miners. True to their enterprising character, many of them remained to con¬tinue the pursuit of fortune with the companies which succeeded the original one.

MODERN TECHNIQUES INTRODUCED

Shortly after the change of ownership, the new company struck the very rich “Rosario” ore body, and thus brought back the bonanza days of the first Conde de RegIa. A period of great prosperity and activity followed, and con¬tinued until 1906. Such was the richness of the ores extracted at this time. that the amount of silver contained in each ton averaged 2,500 grams: an assay which compares very favourably indeed with the 200 grams per ton of the present day.

However, the old Patio process which continued to be used during this period was very inefficient and, as the richer ores were mined out, so it became in¬creasingly difficult to make the operations pay. In 1906 an American Com¬pany (the U.S. Smelting, Refining and Mining Co. of Boston) bought out the

Real del Monte y Pachuca Company. This new enterprise introduced modem methods of mining and processing on a very large scale.

The old patio process was discarded in favour of the much more efficient cyanidation process, the old steam hoists and pumps put up by the Cornish were replaced by modern electric hoists and pumps, and the old stone crushers of Spanish days gave way to up-to-date, electrically driven “Symons” crushers and “Marcy” ball and rod mills. These changes not only revived the faltering mines, but increased production to an enormous extent.

The new process enabled ores of much lower grade to be treated far more profitably than before. The large profits which resulted attracted many other companies to the area, and thus began the period of greatest prosperity and activity. The district became again the world’s largest producer of silver, a position which it holds to this day. With the advent of these .new companies, which included American, British and German firms, the total production rose to relatively huge proportions; it was not uncommon for the daily tonnage of ore milled in those days to reach an average of 4,000 metric tons. It was dur¬ing this period that the greatest part of the 1,200 odd miles of underground workings were formed, a tribute to the tremendous power of the new pneumatic drills, explosives, trains and modem mining methods introduced.

PACHUCA TODAY

After so many centuries of what has been by and large a prosperous mining centre, one could assume that Pachuca would be a well built, clean, and wealthy community. It is sad to relate however that this is not so. There is an air of poverty about the place, its streets are narrow, ill-paved and dirty. Although it is the largest town and the capital of the state of Hidalgo, the population seems to be uninspired, and appears to live in the expectation that the mines will soon be worked out, thus killing forever the hope of a prosperous future.
The enormous fortunes of gold and silver which were won from the mines went to increase the personal fortunes of some men, or to the ever open coffers of the Spanish Government, or to the profits of the various companies which worked the area in later days. Little-very little it would appear-went to Pachuca or its inhabitants.

The mines are still working, but are now entirely owned by a Government controlled company. The last of the foreign owned companies the “Real del Monte y Pachuca Co.” was sold to the Mexican Government in 1947, when it became increasingly obvious that the richest ore reserves had begun to fail, and that it would become much more difficult to make the profits their share¬holders demanded.

Nowadays, the mines are working on ore which is of a very low grade, aver¬aging little more than 200 grams of silver per ton of ore. Only the increasing price of silver has enabled the company to continue its operations, but even so it has been necessary for the Government to provide a subsidy. Ore which in the halcyon days before the second World War was considered to be too low in values, and was dumped or bypassed, is now being mined. It is not un¬common now to see old workings being reopened and stripped of ore which had been left behind as uneconomical in the more prosperous days.

In their efforts to keep the industry alive, the miners and millmen have even turned their attention to the tailings dams left behind after the majority of the values had been extracted from the ore. By putting up the most modem flota¬tion plant of its type in the industry, the Government has enabled some of the old tailings dams to be reworked, and concentrates of silver, lead. zinc and gold tc:> be produced. (Fig. 4).

Whilst this new operation is one which is unlikely to last for more than another ten or eleven years, the extent of the workable tailings dams being limited, it is interesting because the techniques and plant used are the most up to date in the world. Reminiscent of the alluvial tin mines of Malaya, hy¬draulic jets are used to wash down the tailings and transport them to the flota¬tion plant for treatment. Here, after the pulp has been processed so that the mineral bearing sands are separated from the uneconomical slimes, it is passed to flotation cells, where reageants are used to produce foam, the bubbles of which lift the metal sulphides to the surface. They are then skimmed off, dried and shipped for smelting.

The ability of this process to extract from the ore the finest grains of metal sulphides has enabled the rework of tailings from which the cyanidation pro¬cess was unable to make a 100% recovery. To a small extent, it has revitalized the silver mines of Pachuca.

FUTURE PROSPECTS (AS IN 1963)

Whilst many of the inhabitants of the town will have you believe that it will not be long now before the mines will be a thing of the past, the fact remains that there are still in the area huge reserves of very low grade are. There are still one or two optimists who hold that should the price of silver rise to $2.00 per troy ounce, then not only will the future of the mines be assured for a few years more but (they prophesy) the history of the mines of Pachuca will have only just begun . . . . such is the extent of the tremendous quantities of low grade are that remains unexploited. Certainly if some new process of extrac¬tion were to become available, ORe whereby it were possible to treat these low grade ores economically, then there is little doubt that the industry would revive and perhaps even surpass the achievements of previous years.

There are others in the town just as optimistic, but not nearly so numerous as those which hold out future hope through the low grade ores. These are the men who remain true to the pioneering spirit of those who first exploited the mines, the men from Spain and Cornwall who believed in, and discovered, the big bonanza strikes of the past. These super-optimists believe that there still exist, particularly in the relatively underdeveloped region of the Pachuca area to the West, immensely rich are bodies, waiting only for the men with sufficient capital and initiative to develop them.

It is certainly interesting to speculate on the future of the silver mines of Pachuca, but of one thing one can be sure. As the world’s reserves of are dwindle and become scarcer, regions which have been abandoned because the richer veins have been worked out will be reopened and revitalized. Thus, although the future of Pachuca at present appears to be somewhat bleak, someday miners will come back to mine the low grade ores that remain. Whether the present “hand to mouth” operations will last until this happens is a matter for conjecture, but it is unlikely that a mining district that has been in almost continuous production for four centuries will die easily.

CONCLUSION

It is unlikely that many members of R.E.M.E. will have the chance of visiting Pachuca and its mines. However, those who are lucky enough to be posted to the U.S.A. will find it a relatively easy matter to fly down to Mexico City and to travel the sixty odd miles from there to reach this area. Such an enterprise will be worthwhile, not only for the opportunity of indulging in a un¬common holiday in an out of the way place, but also of seeing an engineering project of unusual historical interest.

WORK IN PROGRESS

MEXICAN
MEMORIES