328 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



Ore deposition followed the eriipt'on of lava. The minerals deposited 

 and the manner of their deposition are snch as in the more northerly quick- 

 silver districts were induced by volcanic springs. Though there are now 

 no indubitalde remnants of the volcanic activity which certainly prevailed 

 here since the beginning of the Pliocene, the analogies of the deposit, 

 together with the presence of lava of approximately the same age as the 

 ore, make any theory of deposition excepting from hot sulphur springs 

 improbable. The source of the ore 'will be discussed in a future chapter. 



General fissure system. — Tlie rlu'olite dike, of course, reprcseuTs a deep fis- 

 sure. The length of this dike shown on the map is about twenty thousand 

 feet, but I have followed it beyond the map limit for a considerable dis- 

 tance. The presence and the cliaracter of the range also indicate the 

 existence of an axis of disturbance, though its direction is more or less ob- 

 scured by irregularities in metamorphism and erosion. There can, further, 

 be no doubt from the foregoing description that the cinnabar deposits 

 occur along fissures. The question arises, what connection exists between 

 the fissures upon which the various deposits are found ! It is hardly pos- 

 sible to consider the relative position of the Guadalupe, San Mateo, San 

 Antonio, Enriquita, Providentia, America, and Washington without coming 

 to the conclusion that they form a substantially continuous series of de- 

 posits. If the strike of the Guadalupe, the Enriquita, and the Washington 

 be taken into account this impression is strengthened, for it is easy to draw 

 a continuous line through the deposits which will coincide with the strike of 

 each. This series leaves out the New Almaden and the Cora Blanca. The 

 deep fissures of the New Almaden to the northeast of the Randol shaft are 

 nearly straight, approximately vertical, and strongly marked by slicken- 

 sides, clays, and other evidences of motion. They must be very profound 

 and persistent fissures. They strike nearly for the workings of the Amer- 

 ica. The fissures on the lower levels have been followed for about one 

 thousand feet and to about twenty-two hundred feet in a horizontal direc- 

 tion from the America. I cannot believe that these strong fissures can die 

 out within this distance or that they can greatly change in general direc- 

 tion. They might possibly be replaced by other fissures near to them and 

 parallel with them, the two sets being connected by more or less indistinct 



