SPANISH LOCALITIES. 31 



following a single direction and having a determinate dip, we do not see 

 how one can refuse them tlie name of veins." For my part I am not aware 

 that any definition of vein has been proposed which would exclude the San 

 Francisco and the San Nicolas as they are described, nor can I see how a 

 definition could be given which would exclude these bodies without also 

 excluding the greater portion of known veins. The San Pedro y San Diego 

 would also seem from the descriptions to be a vein-like impregnation, differ- 

 ing from the others chiefly in the size of tlie interstitial cavities, which, for 

 the most part, the cinnabar has filled. 



It is a very remarkable fact that the Almaden mine appears to grow 

 richer as the depth increases. No other known quicksilver deposit exliibits 

 this valuable peculiarity excepting the Idria. It is also interesting to note 

 that the other deposits of the Almaden district have given out in depth, 

 though they occupied a similar position in the same rocks. The relations 

 of cinnabar deposition to depth are thus evidently determined by purely 

 local causes, and not by any general principle governing precipitation. 

 Hence it is quite possible that deposits which grow stronger as distance from 

 the surface increases may be found in any quicksilver district Monasterio 

 and Kuss believe the deposition of ore and the eruption of the diabase to 

 be closely related. 



The province of Granada also contains quicksilver along the soutliern 

 base of the Sierra Nevada. That range is composed of micaceous and 

 chloritic schists and serpentine. The central mass contains little ore of 

 any kind, but gold, lead, copper, zinc, cobalt, and nickel ores are found 

 along its edges. The quicksilver belt has been traced from Torbiscon, in 

 Granada, to Purchena, in Almeria, and runs on a somewhat more northerly 

 course than the Sierra. This strip of country contains numerous veins of 

 cinnabar in talcose schists of Triassic age. The mercurial ore is accom- 

 panied by gray copper, sulphides of nickel and cobalt, and oxides of iron. 

 The veins are small and irregular. In the soft rocks there is a tendency to 

 the diffusion of ore.^ 



Mr. A. Heckmanns, a mining engineer of large experience in the 

 mineral districts of Spain and Algeria, informs me that a distinct vein 



' Guillemia-Tar.iyre, Comptes reudiis Ac.nl. sci., Paris, vol. 100, 1885, ji. 1231. 



