40 MINING INDUSTEY. 



Throughout the central portion of the lode these conchoidal fractures, breaking 

 joints with each other, are of frequent occurrence. 



Beside the minor changes of the east wall, there are certain general curves 

 to the east, which are connected at the extremities with the west wall, forming 

 a series of separate solfataric vents. The Gold Hill group of mines occupies 

 one of these chimneys; the Bullion and a part of the Chollar Potosi, a second; 

 the Virginia group, a third; the Consolidated and Ophir, a fourth. Of those 

 mines lying north of the Ophir, our information is so meager that we are unable 

 to indicate further chimneys. While there is no reason to doubt that the whole 

 vein was formed by one general solfatara, yet, from the difference of miner- 

 alization, both in a quantitative and a qualitative sense, it seems certain that, 

 toward the close of the action, each of these chimneys was a separate outlet. 



Only about 12,000 feet will be analytically described; and, for the conve- 

 nience of study, this central and productive portion is divided into three sec- 

 tions: the Gold Hill group, the Virginia group, and the Ophir group. This 

 is a thoroughly natural division, answering not only to the solfataric chambers 

 but to the bonanzas or ore bodies as they have been found. In general, then, 

 the lode has a longitudinal expansion of 22,000 feet. It is a wedge of material 

 included between an inclined fissure on the west side and a steeper gash com- 

 municating with it on the east. The gash, curving east or west in accordance 

 as the west wall recedes or advances in capes, contains all, or nearly all, of the 

 silver bonanzas. The inclined fissure, though bearing here and there small 

 bunches of silver, is comparatively valueless. Both these fissures are more or 

 less filled with continuous veins of quartz, which are lined on both sides with 

 sheets of clay. Clay also fills all the conchoidal fissures of the propylite horse, 

 and percolates into every water channel within the lode. 



Evidence of long-continued solfataric action is present, not only in the 

 accumulations of quartz and clay, but in the peculiar decomposition of the 

 feldspathic material of the horses. Along the west wall, and separating the 

 vein from the syenite, occur at intervals the metamorphosed and decomposed 

 relics of the dike of andesite which was the starting point of the Comstock 

 lode. Finally, grouped according to interesting rules in the sheets of quartz 

 occupying the gash vein, are the bonanzas or silver ore bodies. Currents of 

 heated waters still penetrate the lode from below, and are unquestionably the 



