28 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



are more recent than the shattering of the mass in which they occur. At 

 Santander, in the same province, cinnabar forms pockets in the lead and 

 zinc ores.^ Casiano de Prado mentions the occurrence of cinnabar and 

 coal together from this province, the coal being unaltered. 



The mines of Almaden are not only the greatest quicksilver mines in 

 the world, but have yielded a product exceeded in value by very few mines 

 of any kind." The name given by the Moors (al maden, the mine) was 

 therefore not inappropriate. Cinnabar from Spain is frequently mentioned 

 by the ancient writers, and the indications are that it came from this localit}'. 

 The accounts reach back to 415 B. C, when an Athenian, Callias by name, 

 is said to have invented and made known a method of separating cinnabar 

 from earthy matter and to have acquired a fortune by mining in Spain. 

 Pliny describes the locality under the name of Sisapo in such a way as to 

 leave no doubt that the mining district of Almaden is meant. A few tons 

 of cinnabar were extracted yearly by the Romans for use as pigment. The 

 mines were certainly worked by the Moors, but no details are now extant. 

 Work on a considerable scale, so far as is known, was first initiated by the 

 German bankers, the brothers Fugger, to whom the mines were farmed in 

 1525 and who retained control till 1645. The demand for quicksilver did 

 not in fact reach large proportions until the discovery of the process of 

 extracting silver from its ores with the help of mercury by Bartolome de 

 Medina, a Mexican miner, in 1557. Work seems to have been prosecuted 

 from the earliest times on portions of the deposits which are still being ex- 

 ploited. Various other deposits within a distance of ten miles have been 



' G. Dewalque: Revue de g<Sologie pour les anuses 1864 et 1865, vol. 4, Paris, 1806, p. 94. 



^The principal authority on the geology of the Almaden mine is Casiauo de Prado, Bull Soc. 

 g^ologique France, 2d series, vol. 12, 1835. The palcoutological portion of this memoir is by Messrs. de 

 Vernenil and Barraude. All subseiiuent writers owe much to this important work. Valuable pa- 

 pers have also been published by the following geologists and engineers: Bernaldez and Figueroa 

 (Memoria sobre las minas de Almaden y Alimidenejos, Madrid); A. Nijggerath (Zeitschr. fiir Berg-, 

 Hiitten- und Salinenweseu im prouss. Staate, vol. 10, 18j2, p. 361) ; Josd de Monasterio y Correa (Rev. 

 univ. mines, vol. 29, 1871, p. 1); H. Kuss (Aunales des mines, Paris, vol. 13, 1878, p. 39); and Caron 

 (Zeitschr. filr Berg-, Hilttcu- und Salinenweseu im preuss. Staate, vol. 28, 1880, p. 126), More general 

 is M. D. de Corlazar's Reseua fisico-geologica de la provincia de Cindad Real. . Prof. R. Helmhacker has 

 investigated the diabase and piedra frailesca of Almaden in Tschermaks mineralogische und petro- 

 graphische Mittheilungen, 1877, and Prof. Salvador Calderon has studied the massive rocks of the dis- 

 trict (Anales Soc. espau. hist, uat., vol. 13, 1884, p. 227). 



The account of Almaden given in the text was compiled before my visit to the spot, and I have 

 added to it only ono or two observations which seemed necessary to obviate uiisnnderatandings. My 

 own results will appear seiiaratcly. 



