Distant by road, and the New Almaden quicksilver mine (the greatest producer in California and long among the greatest in the world) is about 14 m.
The chief metalliferous deposits of the range are of mercury at New Almaden, not far south of San Francisco.
The mercurial ores of the Pacific Coast ranges occur in very irregular deposits in the form of strings and bunches, disseminated through a highly metamorphosed siliceous rod~c. The first locality where the metal was successfully mined was at New Almaden, about 100 m.
The production had steadily fallen to 16,984 flasks in 1908, but in the opinion of the United States Geological Survey this reduction is mainly attributable, in recent years at least, to market conditions, and does not truly indicate the exhaustion of the mines, although the ores now available are of low grades, those of New Almaden having shown a decrease in yield from 36.7% in1850-1851to o~74% in 1895-1896, so that only the greatest metallurgical skill and business economy can sustain the mines against a weak market.
ALMADEN, or Almaden Del Azogue, a town of Spain, in the province of Ciudad Real; situated in mountainous country 55 m.
Almaden, the Sisapon of the Romans, is celebrated for its mercury mines, which were extensively wrought by the Romans and Moors, and are still productive, the ore increasing in richness with the depth of the descent.
The mines ranked with those of Adria, in South Austria, as the most valuable in the world, until the great development of the mercury deposits at New Almaden, in California, U.S.A., between 1853 and 1857.
They were long worked by convict labour, owing to their unhealthy atmosphere; and exemption from military service is granted to miners who have worked at Almaden for two years.
The New Almaden mine (opened in 1824) in Santa Clara county produced from 1850 to 1896 some 73,000,000 pounds.