74 MINING INDUSTEY. 



crushed, very richly charged with silver ores, and very easy to mine. After 

 this had been stoped out for a considerable extent, it v\^as found that the next 

 zone, which lay in immediate contact with it, was composed of large blocks 

 showing no ore upon their outside, but extremely rich in the interior. 

 These fragments, often weighing half a ton, showed not the slightest trace of 

 silver minerals for the first two or three inches from the surface, but the entire 

 middle was one densely-charged mass of rich ore. Lying west of this again 

 was a third and less valuable zone, which, during the earlier years, was left 

 untouched, but which, in the later condition of labor, and the increasing 

 scarcity of ore-deposits, was again looked into, and proved to be a valuable 

 addition to the stoping ground. 



The eastern face of the ore-channel quartz is always more or less inter- 

 mingled with clay. Fragments of quartz may be found embedded a foot deep 

 in the east clay, and masses of clay at an equal distance within the quartz. 

 It is interesting to observe that with all this well-marked longitudinal 

 arrangement there is not the slightest trace of the ordinary comb-structure 

 so characteristic of many fissure veins. It is almost never the case that the 

 zones group themselves in pairs, with the same relations to the opposite walls, 

 which may be seen in the Freiberg veins. 



A careful examination of these bodies induces the belief that the fissures 

 were all filled at one time with uniform masses of quartz, and that the parallel 

 arrangement has been afterward given them by the combined chemical and 

 dynamical action to which they have been exposed. There is not a particle 

 of evidence that the quartz and ore were successively deposited in layers upon 

 the fissure walls from lateral secretion in situ. The quantitative relations of 

 V the quartz to the surrounding horse and wall-material, together with the 



analyses which are given further on in this section, preclude any such idea. It 

 is evident that the fissures were filled with quartz from some deep-seated 

 source, and that the masses when formed have been afterward subjected to 

 dynamical action sufficient to crush them into minute fragments, without in 

 any case faulting them. The writer believes that to the disturbance 

 which gave vent to the andesite eruptions must be attributed the origin 

 of the Comstock lode, and, in consequence, we have ample subsequent move- 

 ment to account for any interior dislocation and dynamical action that has been 



