28 SILVER LEAD DEPOSITS OF EUREKA, NEVADA. 



sonable doubt, however, that the fissure, which in the Jackson and Phcenix 

 carries rhyolite, is identical with that which in the K. K. and the Eureka 

 carries calcareous clay. The fissure is intersected by drifts in over twenty 

 places, all of which correspond in position with that which the fissure would 

 be supposed to occupy from an examination of the exposures taken singly. 

 Better proof than this of the identity of a surface is rarely met with in 

 mines. When there are many fissures or slips it is not always an easy mat- 

 ter to distinguish one from the other, for one may have given o^^t and 

 another one taken its place, or faults might have occurred which would 

 bring another fissure into the place where the first was to have been ex- 

 pected. This could not be the case in the present instance, as there is no 

 strong fissure within several hundred feet at any rate of the one in ques- 

 tion. This is shown by the explorations which have been carried on in the 

 "front limestone" on the sixth level of the K. K. and in the cross-cut to the 

 Locan shaft in the Eureka mines. So, too, the contact of an irregular sur- 

 face, like the contact of quartzite and limestone, requires more proof than 

 that of a regular one. In the present case the evidence is amply sufficient 

 not only to prove the continuity of the fissure, but its unusual regularity. 

 If the change in the material composing the filling of the fissure had oc- 

 curred at the single bend of any importance in this fissure, which appears 

 in the Jackson, a drift along its course might have been necessary to estab- 

 lish the identity of the two branches. The rhyolite, however, gives out 

 between the workings of the Phoenix and K. K., and to the northwest of 

 this point is replaced by clay identical with that which fills the fissure in 

 the Eureka and K. K., so that the disappearance of the rhyolite forms no 

 argument against the continuity of the fissure. This clay also, as found in 

 the Eureka and K. K., is partly derived from the rhyolite, and is merely the 

 decomposed feldspar of that rock mixed with crushed limestone. 



The main fissure at the American shaft. The fil'St poillt wlld'e the maill fisSUl'e is 



noticeable at the southeast end of the Ruby Hill fault is at the American 

 shaft, which is situated over 400 feet south of the Jackson hoisting works. 

 The shaft, which is 25 feet deep, is sunk in Pogonip limestone. From near 

 the bottom of this shaft a cross-cut has been driven to the quartzite in a 

 southwesterly direction. In this cross-cut, 10 feet from the shaft, the main 



