Almadén: the mercury of the Indies, and the ledger its own state kept
The oldest known mercury mine in the world became, after about 1550, the European supply for a Mexican invention: Bartolomé de Medina's silver amalgamation. By 1861 a Spanish government memoir could argue that almost the whole consumption of Almadén's quicksilver was the treatment of American silver ores by the patio system. The same memoir prints the miners' hospital returns for 1844–1855 and the physician's account of what mercury did to the men.
Why this wins its question: Almadén appears in English-language accounts of the silver economy as a place-name in a supply chain, and in histories of occupational medicine not at all — Ramazzini takes the whole eighteenth century. This object puts the two together from the mine's own state memoir of 1861, read page by page: the sentence in which a government arguing for privatisation concedes that its mercury exists for American silver, the sentence in which it calls the vapour undeniable, the hospital physician's catalogue of what mercury does to a body, and the twelve-year hospital return with the deaths counted and the unrelated cases subtracted. The counterpoints are on the record beside them: Ramazzini's priority, and the fact that the Parés monograph itself could not be opened here.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
The mines of Almadén are more than two thousand years old and the oldest known in the world; the Romans were the first to extract mercury there systematically. Production had two stages — underground extraction of the cinnabar ore, then distillation in furnaces by burning the cinnabar and condensing the resulting mercury vapour.
What turned an old mine into a strategic one was an American invention. Around 1550 Bartolomé de Medina developed a technique that benefited silver minerals through amalgamation with mercury; this caused a dramatic increase in the demand for mercury, and the technique extended to the mines of New Spain and later to Peru.
Three centuries later the dependence still defined the mine, and the Spanish state said so in print. Bernáldez and Rúa Figueroa, arguing in 1861 that Almadén was the first property the crown should think of selling, rest the case on the fact that the almost entire consumption of quicksilver — or at least the greater part of it — was limited to the treatment of the silver minerals of America by the system of patios, and that the day would come when those ores would be worked by the methods of Becquerel, Ziervogel or Augustin and the miners would stop buying an article they always had to purchase at a high price.
The same memoir states the hazard without hedging: the existence of mercury vapour in the atmosphere of the Almadén underground is "un hecho de todo punto innegable". A short walk through the upper levels where ventilation is poor or the temperature a little high is enough to produce at once an unpleasant taste with abundant salivation and later inflammation of the gums and ulcers in the mouth, effects that medical science recognises under the name of thialismo.
The authors then name their evidence and their opponent. The data supplied by the establishment's Hospital and the death books of the villa are, they write, the most painful and most eloquent proof of the ills that weigh on those miners, and the highest protest against the hard and unpremeditated assertions of the illustrious Bowles in his Geografía física de España. A state memoir arguing against a published naturalist that its own mine was as unhealthy as the miners' books said is not the shape a whitewash takes.
The clinical account is given to a named physician rather than asserted by the engineers. Gervasio Sánchez Aparicio, physician and surgeon of the miners' Hospital, reports that no field labour and no ordinary industry demands the physical aptitude the Almadén mines do; that the healthiest and most vigorous man loses his freshness and vigour within two years of underground work, strong and athletic constitutions turning weak and delicate and readily disposed to every class of disease; and that the general affection — stupor, or cramps and continuous pains in parts of the body or the whole of it — is so universal that with very few exceptions all the workers suffer it, dulled from their youth and lacking the strength and agility to manage by themselves.
Worse than that, in his account, is the absorption itself: mercury taken up over the whole surface of the body and introduced into the stomach and the airways gives rise to skin affections, to deep and very ill-charactered ulcers of the mouth with loss of the teeth, and finally to irritations or intoxications of the digestive apparatus so grave in malignity and resistance that they end the sufferer's life prematurely and after terrible suffering. Chest affections, from air continuously fouled by gases and the impalpable dust of the cinnabar itself, rank second among the diseases that torment the miners of Almadén.
The memoir then does the thing that makes it evidence rather than testimony: it counts. The first of the tables accompanying the physician's report covers the miners assisted in the establishment's Hospital from 1844 to 1855, classified as internal or medical and external or surgical. Of 5,047 internal cases the authors discard 2,281 as diseases of a different nature due to common causes, leaving 2,766 in the category attributable to the work, of whom 459 died. Of 2,701 external cases, 332 are ordinary affections independent of mine work, leaving 1,369.
That record has an eighteenth-century ancestor at the same mine, and the international literature knows it. A chronological review of the occupational-disease literature, written by Slovak authors surveying the whole field, lists José Parés y Franqués (1720–1798) and his "Catástrofe morboso de las minas mercuriales de la villa de Almadén del Azogue" among the works of the discipline. The counterpoint belongs in the same sentence: the same review names Bernardino Ramazzini, who died in 1714, as the acknowledged father of occupational medicine, and Parés wrote after him, not before.
The exposure at Almadén was still extreme when it was finally measured with instruments. Over 1950 to 1994 peak concentrations reached 2.26 milligrams per cubic metre in air during drilling and 3.37 at the furnaces, 2,194 micrograms per litre in urine and 374 in blood. Mining ceased in 2001 and metallurgical activity in 2004.
What is not evidenced here should be said plainly. The pages of the 1861 memoir that were opened say nothing about the convict and forced labour used at Almadén in earlier centuries, and nothing about the quantities shipped to America or the terms of the mercury monopoly; the 2007 exposure study explicitly contains no discussion of forced labour, of the miners' hospital or of shipments to the Americas; and the monograph of Parés y Franqués could not be opened from this container, so its contents are not described here and its standing rests on one line of a general review.