THE ORE DEPOSITS. 73 



mountain has been much less than those in the hill, and the caves have been 

 smaller and less numerous. 



Fissures and faults. — Both Prospect Mountain and Ruby Hill are traversed 

 by numerous fissures or faults. The more important and persistent of these 

 follow the course of the axial plane of the anticlinal fold, which, in the case 

 of Prospect Mountain, has a north and south course, and in the case of 

 Rubv Hill, a northwest by southeast course, and dip away from it. There 

 are, however, a great number of cross-fissures. The former seem to have 

 been faults accompanied by upward movements, while the latter show tha*: 

 there has been lateral as well as vertical pressure exerted during their for- 

 mation. As a rule these fault-fissures are mere seams, although they may 

 extend several hundred feet in every direction. Sometimes, however, they 

 are of considerable width, and have been partially filled with bowlders 

 broken from the walls and de"bris washed in from above. They occasion- 

 ally contain ore and in several cases assume the appearance of fissure veins. 

 Where fissures containing lead ore occur in limestone in Cumberland, Der- 

 byshire, and in many parts of Europe, the country is very much less dis- 

 turbed than it is in Eureka, and the mountain folds are much less sharp. 

 Examples of fissure veins are not absolutely wanting at Eureka. There is 

 one in the Banner mine which crosses the axis of fold of Prospect Mount- 

 ain, and is remarkably regular for a lode in limestone The east ore body 

 of the Richmond mine begins in the Tip Top claim, one of the location 

 claims of the Richmond Company, and extends down to the Potts chamber 

 on the "compromise line." A fissure seems to exist through the entire area 

 thus indicated, and though the ore does not always fill the fissure and though 

 the fissure itself often shrinks to a mere seam, the whole occurrence can 

 properly be regarded as a fissure vein. In the Ruby-Dunderburg there is 

 an instructive deposit which in some portions fills a clean-cut fissure a foot 

 or more in width, and in which at some points the ore penetrates the hang- 

 ing wall in large irregular outgrowths from the vein, which have supplied 

 most of the ore. 



caves in connection with ore bodies. — Caves are found in many places in the lime- 

 stone and are of frequent occurrence in connection with ore bodies; in fact, 

 no large ore bodies have been found which had no caves over them; but 



